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nil  il  li  ill!!!!!! 


GIFT  or 


NEW  PHYSICAL  GEOGRAPHY 


THE  MACMILLAN  COMPANY 

NEW  YORK    •    BOSTON   •    CHICAGO 
DALLAS    •    SAN    FRANCISCO 

MACMILLAN  &   CO.,  Limited 

LONDON  •  BOMBAY  •  CALCUTTA 
MELBOURNE 

THE  MACMILLAN  CO.  OF  CANADA,  Ltd. 

TORONTO 


Fig.   1.— The  Colorado  Canyon. 


Frontispiece. 


NEW 


PHYSICAL  GEOGRAPHY 


BY 


RALPH    S.    TARR,    B.S. 

PROFESSOR    OF    DYNAMIC    GEOLOGY    AND    PHYSICAL    GEOGRAPHY 

AT    CORNELL    UNIVERSITY 


AUTHOR    OF     "ECONOMIC    GEOLOGY    OF    THE    UNITED    STATES,"     "ELEMENTARY 
GEOLOGY,"    "physical    GEOGRAPHY    OF    NEW    YOilK,  fT!\.TE,"    ETC,   - 
AND    CO-AUTHOR    OF    "  TARR-MCMURRY    GEOdDA^VHiES'"  .  .' 


THE   MACMILLAN    COMPANY 

LONDON:  MACMILLAN  &  CO.,  Ltd. 
1920 

AU  rigJvU  reserved 


T  3  6- 


Copyright,  1903, 
By  the  MACMILLAN  COMPANY. 


Set  up  and  electrotyped.     Published  January,   1904.     Re- 
printed,    May,     1904;    January,    August,     October,     1905; 
•     ■   ,'.  April*  jls^c^embe^,    1906;   September,    1907;   January,    Octo- 

';  %''         lie'r','' iJo^V 'jWary,     1909;    January,    July,     1910;    April, 
August,    1911;^FQbwary,    1912;    September,    1912;    March, 
.  ',  'I  '.[I'Mi'i^l  5913'  Jamuary,   April,    1914;   March,    1915;   August, 
,1  .'   J/r  •W15;'P\brna^y,«  Jify,  November,  1917. 


, 


PREFACE. 

Nearly  eight  years  ago  the  author  published  his  Ele- 
mentary Physical  Geography,  which  was  followed,  two 
years  later,  by  his  First  Book  of  Physical  Geography, 
really  a  presentation,  in  briefer  and  more  elementary  form, 
of  the  matter  contained  in  the  earlier  book.  The  growth  of 
the  science  of  physical  geography,  —  which  has  been  little 
short  of  marvelous, — the  rapid  advance  in  rank  which  the 
subject  has  won  for  itself  in  the  schools,  and  the  new 
ideas  and  new  methods  of  presentation  which  have  come 
to  the  author,  have,  for  several  years,  made  him  desirous 
of  undertaking  a  revision  of  one  or  both  of  his  texts. 
When,  however,  this  desire  was  given  concrete  form,  and 
systematic  attention  was  paid  to  the  nature  of  the  revi- 
sion, it  became  evident  that  it  would  mean,  not  merely  a 
revision,  not  even  a  mere  rewriting,  but  a  complete  destruc- 
tion of  the  old  book  and  the  construction  of  an  entirely 
new  book,  different  in  plan,  in  scope,  and,  in  many  respects, 
in  subject-matter.  Then,  for  the  first  time,  arose  the  idea 
that,  since  it  would  be  a  new  book  in  fact,  it  would  be  bet- 
ter to  issue  it  as  such  than  as  a  new  book  under  an  old  title. 
One  important  reason  for  reaching  this  decision  was  the  fact 
that  both  the  Elementary  and  First  Book  are  in  wide  use. 
A  field  for  them  evidently  exists,  and  it  appears  hardly  wise 
to  destroy  absolutely  that  for  which  there  is  a  demand. 
Twelve  editions  of  the  Elementary  have  been  published 
and  fifteen  of  the  First  Book. 

The  teaching  of  physical  geography  is  still  in  its  expe/^j. 

45^952 


vi  PREFACE. 

mental  stage,  and  it  is  the  opinion  of  many  teachers  that 
the  ideal  method  of  presentation  has  not  yet  been  proposed, 
notwithstanding  the  several  excelibnt  texts  which  have 
appeared.  The  New  Physical  Geography  is  still  another 
effort  to  solve  the  problem  of  how  best  to  present  the  sub- 
ject to  beginning  students.  The  author  does  not  flatter 
himself  that  he  has  produced  the  ideal ;  his  only  hope  is 
that  he  has  done  better  in  his  third  attempt  than  he  did 
in  the  other  two. 

In  the  New  Physical  Geography,  treatment  of  the  lands 
has  been  placed  before  that  of  air  and  ocean  because  so 
many  schools  commence  the  study  in  the  fall  and  take 
classes  into  the  field.  The  chapters  on  atmosphere  and  ocean 
have  been  given  less  space  than  in  the  author's  previous 
books  ;  yet  all  topics  of  distinct  importance  are  treated  with 
sufficient  fullness  to  make  them  clear.  Certain  subjects  that 
are  not  universally  deemed  necessary  parts  of  physical  geog- 
raphy are  treated  in  appendixes ;  it  is  the  belief  of  the 
author  that  each  of  these  should  be  studied. 

Perhaps  the  most  decided  difference  between  the  New 
Physical  Geography  and  the  author's  other  books  lies  irr. 
the  introduction  of  a  much  fuller  treatment  of  life  in  its 
relation  to  the  land,  air,  and  ocean,  the  human  interest  ol 
each  topic  being  emphasized.  This  has  been  done  through- 
out the  text  and,  at  the  end  of  the  book,  in  a  series  of 
chapters  devoted  to  that  subject  exclusively. 

Especial  pains  has  been  taken  to  illustrate  the  book  fully. 
It  is  believed  that  an  illustration,  properly  selected,  is  of 
the  very  highest  value,  —  the  best  substitute  for  the  object 
itself.  Every  illustration  in  the  book  is  introduced  for  use, 
and  almost  every  one  is  referred  to  at  least  once  in  the  text. 
Among  these  illustrations  half  tones  of  photographs  predomi- 
nate, for  they  alone,  of  all  forms  of  illustration  commonly  in 


1  BE  FACE.  vii 

use,  present  the  whole  truth.  In  order  that  they  shall  be 
distinct,  the  half  tones  are  all  printed  on  glossed  paper  ;  but 
to  avoid  giving  the  book  undue  weight,  and  to  eliminate  the 
trying  effect  of  glossed  paper  on  the  eye,  the  text  is  printed 
on  a  light-weight,  dull-finished  paper  and  the  half  tones  on 
inserted  sheets.  Besides  half  tones  there  are  many  diagrams, 
maps,  and  block  drawings,  the  latter  prepared  by  C.  W. 
Furlong  of  Cornell  University. 

As  aids  to  the  study  of  the  text,  a  brief  Summary  is  given 
at  the  close  of  each  section,  and  a  Topical  Outline  and  a  set 
of  Review  Questions  are  placed  at  the  end  of  each  chapter. 
It  is  believed  that  the  great  majority  of  teachers  will  wel- 
come these  aids.  No  teacher  will,  of  course,  be  content  to 
follow  the  questions  absolutely  and  without  modification ; 
the  individuality  of  the  teacher  will  appear  here,  as  else- 
where. But  these  summaries,  topics,  and  questions  cover  the 
essentials  in  the  text ;  and  their  use  as  a  basis  for  work,  with 
such  modifications  and  additions  as  may  be  deemed  necessary, 
will  be  a  far  lighter  task  than  the  production  of  an  entire 
series  by  the  teacher.  Thus,  relieved  of  a  form  of  drudgery, 
time  will  be  available  for  the  expenditure  of  energy  in  more 
profitable  lines. 

In  most  of  the  better  schools  physical  geography  is  fast 
becoming  a  laboratory  science,  and  this  is  the  position  it 
must  eventually  take  wherever  taught.  In  the  absence  of 
a  laboratory  manual,  many  teachers  find  it  difficult  to  plan 
a  laboratory  course.  That  this  is  so  is  evident  from  the 
many  letters  that  the  author  receives  on  the  subject.  With 
this  in  mind,  a  series  of  Suggestions  is  appended  to  nearly 
every  chapter,  and  one  appendix  is  devoted  to  maps  and 
laboratory  equipment,  another  to  field  work.  From  these 
suggestions  any  teacher  will  be  able  to  select  some  for  use. 
It  ir  hoped  that  they  may  serve  as  an  incentive  to  additionaJ 
laboratorv  and  field  work. 


Vlll  PREFACE. 

A  very  large  number  of  teachers  have  given  the  author 
the  beneht  of  their  experience  in  the  form  of  suggestive 
criticism.  To  all  of  these  teachers  —  making  a  list  far  too 
long  to  print  here  —  the  author  is  greatly  indebted  for  their 
kindly  interest.  They  have  helped  to  shape  the  plan  of  the 
book.  Among  these,  however,  are  several  whose  suggestions 
were  of  such  marked  value  that  their  aid  must  be  acknowl- 
edged individually  :  Frank  Darling,  Chicago  Normal  School ; 
C.  S.  Jewell,  Lake  View  High  School,  Chicago;  E.  C.  Case, 
Milwaukee  Normal  School ;  L.  O.  Towne,  Haverhill,  Mass.  ; 
Emerson  Rice,  Hyde  Park,  Mass.  ;  H.  L.  Rand,  Dedham, 
Mass.  ;  H.  L.  F.  Morse,  Troy,  N.Y.  ;  Miss  Agnes  Brown, 
Rockford,  111.  ;  and  James  A.  Barr,  Stockton,  Cal.  Special 
acknowledgment  must  also  be  made  to  Lawrence  Martin  of 
Cornell  for  valuable  assistance  and  suggestion  during  the 
preparation  of  the  book. 

It  goes  without  saying  that  the  author  is  profoundly 
indebted  to  the  host  of  workers  in  physiography,  from  whom 
he  has  drawn  so  much  inspiration,  suggestion,  and  fact  : 
Gilbert,  Davis,  Powell,  Geikie,  Penck,  de  Lapparent,  Russell, 
Shaler,  Dutton,  Chamberlin,  Hayes,  Campbell,  Salisbury, 
Brigham,  Dodge,  Dryer,  and  many  others.  From  the  writ- 
ings of  these  physiographers  the  author  has  culled  whatever 
seemed  to  him  suited  to  a  scheme  of  elementary  instruction  ; 
and  so  numerous,  and  often  so  unconscious,  is  the  influence 
of  these  fellow-workers,  that  8[)ecific  acknowledgment  would 
be  quite  impossible.  Doublless  the  most  profound  influence 
upon  the  author  is  that  of  liis  two  teachers.  Professors 
Shaler  and  Davis,  tlie  importance  of  which  to  him  cannot  be 
overestimated.  Together  with  other  physiographers,  the 
author  further  recognizes  in  Professor  Davis  a  leader  in 
American  physiography,  from  whom  even  some  of  the  fun- 
damental principles  of  the  subject  have  been  derived.     An 


PREFACE.  IX 

examination  of  the  following  pages  would  show  the  influence 
of  this  physiographer  in  many  places,  an  influence  not  con- 
fined to  the  pure  science,  but  extending  to  the  pedagogy  of 

the  subject  as  well. 

RALPH   S.   TARR. 
Ithaca,  N.Y.,  July  21,  1903. 


CONTENTS. 


CHAPTER 
I. 

The  Earth  as  a  Planet        .... 

PAGE 

-• 

1 

II. 

General  Features  of  the  Earth 

.      13 

XII. 

Changes  in  the  Earth's  Crust    . 

.      31 

IV. 

KiVERS  AND  River  Valleys   . 

.      50 

V. 

Plains,  Plateaus,  and  Deserts   . 

72 

VI. 

Mountains 

.       93 

VII. 

Volcanoes,  Earthquakes,  and  Geysers 

112 

VIII. 

Glaciers  and  the  Glacial  Period 

.     137 

IX. 

Lakes  and  Swamps 

.     160 

X. 

The  Ocean         

.     173 

XL 

Shore  Lines 

.     203 

XII. 

The  Atmosphere 

.     229 

XIII. 

Winds  and  Storms  ..... 

,     255 

XIV. 

Weather  and  Climate  .... 

.     275 

XV. 

Physiography  of  United  States 

.     298 

XVL 

Rivers  of  United  States       .... 

.    320 

XVII. 

Distribution  op  Plants 

.     336 

XVIII. 

Distribution  of  Animals       .        ,        .        .        , 

.    353 

XIX. 

Man  and  Nature     

k 

369 

CONTENTS, 


XI 


APPENDIXES. 


A.  Revolution  of  the  Earth  . 

B.  Latitude  and  Longitude 

C.  Common  Minerals  and  Rocks 

D.  Geological  Ages     . 

E.  Tides  .        .        ,        .        . 

F.  Magnetism 

G.  Meteorological  Instruments 
H.  Weather  Maps 

I.  Maps  .... 

J.  Laboratory  Equipment 

A.  Field  Work 

L.  Reference  Books    . 

Index   •   •   .   • 


PAGE 

.  397 

.  402 

.  406 

.  415 

.  416 

.  418 

.  420 

.  42d 

.  428 

.  43". 

.  442 

.  443 


ACKNOWLEDGMENT   OF   ILLUSTRATIONS. 

Aside  from  the  illustrations  acknowledged  in  the  list  below,  and  a  few 
acknowledged  beneath  the  pictures  themselves,,  a  number  of  photographs 
were  obtained  from  a  great  variety  of  sources,  American  and  foreign.  Many 
of  the  photographs  were  taken  by  the  author  ;  many  are  from  the  collection 
in  the  department  of  Physical  Geography  at  Cornell  University.  For  photo- 
graphs, especial  acknowledgment  is  due  Mr.  J.  0.  Martin,  formerly  of  Cornell 
University  ;  William  H.  Rau,  Philadelphia  ;  F.  J.  Haynes,  St.  Paul ;  Detroit 
Photographic  Co.,  Detroit ;  and  S.  R,  Stoddard,  Glens  Falls,  N.Y.  The 
topographic  maps  are  made  from  the  United  States  Geological  Survey  topo- 
graphic sheets  ;  the  weather  maps  and  many  of  the  diagrams  of  temperature, 
etc.,  are  based  upon  maps  and  data  obtained  from  United  States  Weather 
Bureau  Publications.  Most  of  the  relief  maps  are  reproduced  from  models 
made  by  E,  E.  Howell,  Washington  ;  many  of  the  drawings,  especially  the 
block  drawings,  are  by  C.  W.  Furlong,  of  Cornell  University.  The  animal 
pictures  and  the  map  and  picture  of  the  races  of  man  are  by  Matthews- 
Northrup  Co.,  Buffalo.  A  number  of  illustrations  were  taken  from  earlier 
books  by  the  author. 

Of  the  remaining  illustrations  a  few  are  made  from  copy  whose  source 
could  not  be  ascertained.  Illustrations  taken  from  books,  or  based  upon 
maps  or  diagrams  in  books,  and  a  few  photographs  not  purchased  from 
dealers,  are  acknowledged  in  the  following  list :  — 

Abbe,  C,  Jr.  (Maryland  Weather  Bureau),  122,  123  ;  (Maryland  Geological 

Survey),  463. 
Agassiz,  A.  (Three  Cruises  of  the  Blake),  324,  325,  343. 
Bartholomew  (Physical  Atlas,  Meteorology),  407,  435. 
Von  Bebber  (Lehrbuch  der  Meteorologie) ,  425. 
California  State  Mineralogist's  Report,  238. 
Calvin,  Prof.  S.,  Des  Moines,  la.,  88. 
Canadian  Geological  Survey,  46. 
Carney,  F.,  Ithaca,  N.Y.,  282. 
Challenger  Reports,  311,  314,  317,  318,  320. 
Chamberlin,  T.  C.  (based  upon  his  map),  United  States  Geological  Survey, 

269. 
Chamberlin  and  Leverett  (American  Journal  of  Science),  295.  ' 

Darton,  N.  H.,  United  States  Geological  Survey,  115. 
Daubeny,  C,  Volcanoes,  210. 

zii 


ILL  US  TEA  TIONS.  xiii 

Diller,  J.  S.,  United  States  Geological  Survey,  215,  219,  235. 

Drake,  N.  F.  (California  Model),  114,  350. 

Emerson,  P.   (New  England   Supplement,  Tarr  &  McMurry  Geographies), 

454,  456. 
Fairchild,  H.  L.  (New  York  Geological  Survey),  273. 
Foerste,  A.  F.  (Proceedings  Boston  Society  Natural  History),  1G8. 
Friez,  J.  P.  (Dealer  in  Meteorological  Instruments),  Baltimore,  Md.,  561, 

564,  565,  566. 
Gardner,  J.  L.,  Boston,  Mass.,  286,  328,  329,  331,  355,  361. 
Gilbert,  G.  K.  (Henry  Mountains),  164,  233;  (Niagara  Commission),  277; 

(Lake  Bonneville),  United  States  Geological  Survey,  301. 
Harden,  E.  B.  (Pennsylvania  Model),  172. 
Harvard  College  Observatory,  2,  5. 
Hayden,  E.  (National  Geographic  Magazine),  426. 
Hayden,  F.  V.  (Geological  Survey  Territories),  138,  140,  159. 
Heim,  A.  (Mechanismus  der  Gebirgebildung) ,  156. 
Hill,  K.  T.  (Topographical  Atlas,  Texas),  United  States  Geological  Survey, 

96,  144. 
Holden,  E.  S.  (Memoirs  National  Academy  of  Sciences),  382. 
Hovey,  E.  0.  (American  Museum  Natural  History),  New  York,  197,  198. 
Ikenberry,  W.  L.,  Mt.  Morris,  111.,  420,  422. 
Johnston-Lavis,  H.  J.,  195. 

Jones,  Thomas  (Earth  Model),  Chicago,  111.,  313. 
Jukes-Browne,  A.  J.  (Handbook  of  Physical  Geology),  344. 
Kent,  H.  Saville-  (Great  Barrier  Reef),  380. 
Koppen  (Atlantischen  Ozean),  409,  410. 
Libbey,  Prof.  W.,  Jr.,  266,  272,  486,  524. 

McAllister,  T.  H.  (Dealer  in  lantern  slides).  New  York,  484,  490,  496. 
Mexican  Boundary  Commission,  Report,  147. 
Mills,  F.  S.,  Andover,  Mass.,  92. 

Milne  and  Burton  (Great  Earthquake  of  1891  in  Japan),  239. 
Nasmyth  and  Carpenter  (The  Moon),  14. 
Newberry,  J.  S.  (Popular  Science  Monthly),  462. 
Penrose,  R.  A.  F.,  Jr.,  Philadelphia,  126. 

Powell,  J.  W.  (Explorations  of  the  Colorado  River),  36,  59,  139,  478. 
Ratzel,  F.  (History  of  Mankind),  489,  491,  493,  529,  534,  538,  546. 
Ried,  Prof.  H.  F.,  Baltimore,  Md.,  250. 
Ritchie,  J.,  Jr.,  Boston,  171,  284. 

Russell,  Prof.  I.  C,  Ann  Arbor,  Mich.,  252,  256,  257,  258. 
Shaler,  Prof.  N.  S.  (United  States  Geological  Survey),  90,  305. 
Shedd,  S.  (Washington  Model),  476. 
Sigsbee  (Deep-sea  Sounding,  United  States  Coast  Survey),  310,  312. 


xi  V  ILL  USTRA  TIONS. 

Symons  (Eruption  of  Krakatoa) ,  220. 

Taylor,  F.  B.  (Dryer's  Studies  in  Indiana  Geography),  280,  281. 

United  States  Coast  Survey,  334,  336,  560. 

United  States  Fish  Commission,  342. 

United  States  Geological  Survey,  1,  38,  45,  51,  55,  148, 154,  214,  231,  260,  307, 

472,  498,  531. 
United  States  Hydrographic  Bureau,  427. 

United  States  Weather  Bureau  (Monthly  Weather  Review),  402. 
Upham,  W.  (Lake  Agassiz),  United  States  Geological  Survey,  130. 
Ward,  R.  de  C,  Series  of  Cloud  Slides,  402,  423. 
Webster,  Commander  H.,  United  States  Navy,  543. 
Willis,  B.,  United  States  Geological  Survey,  39,  40,  '48. 
Williston,  Prof.  S.  W.,  Lawrence,  Kan.,  64,  127. 


INTRODUCTORY. 

Man  is  vitally  dependent  upon  air,  water,  and  earth.  The 
air  supplies  oxygen  for  breathing  and  for  fire;  it  supplies 
carbon  dioxide  to  plants;  it  brings  vapor  for  rain;  and  its 
presence  and  movements  profoundly  affect  climate. 

The  ocean  is  the  source  of  vapor;  it  furnishes  many  kinds 
of  food  fish;  it  is  the  highway  of  an  ever  increasing  com- 
merce; and  it  influences  the  climate  of  every  land. 

The  lands  furnish  a  home  for  man;  they  are  mantled  with 
a  soil  in  which  the  food  plants  grow;  and  from  the  rocks  are 
obtained  mineral  fuels,  building  stones,  and  metals.  Both 
plant  and  animal  life  are  greatly  influenced  by  the  forms 
of  the  land  and  the  distribution  of  land  and  water. 

The  sun  is  also  of  vital  importance,  for  its  heat  and  light 
make  life  on  the  globe  possible.  The  heat  sets  the  air  in 
motion,  forming  winds  which  bring  rain,  modify  climates, 
and  start  waves  and  currents  in  the  ocean. 

The  movements  of  the  earth  —  rotation  and  revolution  — 
are  also  important.  .Rotation  brings  day  and  night,  which 
influence  the  habits  of  men,  animals,  and  plants.  Revolu- 
tion causes  seasons,  which  have  a  still  greater  effect  on  life. 

Plants,  animals,  and  mankind  have  adapted  themselves  in 
a  wonderful  manner  to  the  soil,  climate,  and  other  features  of 
their  surroundings.     Most  animals  and  plants  live  either  in 


XVI  INTRODUCTORY. 

the  water  or  on  the  land;  but  some  have  adopted  the  air 
as  their  home,  while  others  have  taken  to  life  underground, 
though  always  near  the  surface. 

Air  and  water  are  ever  changing;  the  lands  are  also 
changing,  though  more  slowly;  and  plants  and  animals  are 
varying  in  their  relation  to  air,  ocean,  and  land.  These 
changes  have  a  profound  effect  on  man,  and  it  is  therefore 
important  to  study  about  them.  ' 

Such  a  study  is  known  as  Physical  Geography,  which  may 
be  defined  as  the  study  of  the  physical  features  of  the  earth 
and  their  influence  on  man. 


NEW   PHYSICAL   GEOGEAPHY. 


o'i^ioo- 


CHAPTER   I. 


THE   EARTH  AS   A   PLANET. 

1.    Shape  of  the  Earth.  —  When  we  look  at  the  full  moon 

we  see  clearly  that  it  is  a  sphere  in  the  heavens  (Fig.  2). 

If  we  could  stand  on  the 

moon     and    look    at    the 

earth,  we  would   see   that 

it,  too,  is  a  sphere.      But 

the  earth  is  a  much  larger 

sphere     than     the     moon 

(Fig.  3). 

Over  two  thousand  years 

ago  it  was  known  that  the 

earth   was   a   sphere;    but 

this    was   later   forgotten, 

and   for  a   long    time    the 

earth   was  believed  to  be 

flat.       Before  the  time  of 

Columbus,   navigators  im- 
agined all  sorts  of  terrors  at  the  edge  of  a  flat  earl^  ;  and 

Columbus  had  diflcMlty 
in  finding  sailors  who 
were  willing  to  face 
these  imaginary  terrors. 
Columbus's  voyage 
helped  to  bring  into 
prominence  the  o^d 
proofs  that  the  earth 
is  a  sphere. 


B  iG.  2.  —  The  moon. 


EarCB, 


I  Moon  2I5o\ 


7900 


Fig.  3. — Relative  size  of  earth  and  moon. 
The  figures  are  the  diameters  in  miles. 


N.TiJTr  PHYSICAL   GEOGRAPHY. 


Fig.  4.  —  The  curved  ocear  surface. 


No  matter  where  one  may  stand  on  the  seashore,  or  on  a  vessel 

m  the  open  ocean,  he  may  find  proof  that  the  earth's  surface  is 

curved  (Fig.  4).  The 
sails  and  smoke  of 
distant  ships  are  seen 
while  the  hulls  are 
hidden  behind  the 
curvature  of  the 
earth  (Fig.  6).  As  the 
ship  comes  nearer, 
more  and  more  of  it 
is   seen.     This  does 

not   prove   that  the  earth  is  a  sphere,  for  other  curved  bodies, 

such  as  an  egg-shaped  one,  would  produce  the  same  effect. 
That  the  earth  is  spherical 

is  now  proved,  and  its  size  and 

exact  form  have  been  meas- 
ured by  scientists.    Travelers 

have  gone  around  it  in  various 

directions,  and  it  is  known 

how  far  one  must  travel  to 

return  to  the  starting  point. 

Among  the  proofs  that  the 

earth   is    a   sphere,  and  one 

known  to  the  ancient  Greeks, 

is  that  furnished  by  eclipses  of 

the  moon.     Such  an  eclipse  is 

caused  by  the  earth's  shadow 

thrown   on  the  moon    when 

the  earth  comes  between  the 

sun  and  moon.,     This  shadow 

is  always  bounded  by  part  of  a  circle  (Fig.  5).     If  the  earth  were 

not  a  sphere  this  could  not  be  so,  for  in  some  positions  its  outline 

would  be  certani  to  show  the  true  form. 


Fig. 


—  Curved  shadow  ul  the  earth  dur 
iug  au  eclipse  of  the  moon. 


Fio.  G.  — To  show  why  part  of  a  distant  ship  is  hidden.     The  stva.ght  line  .o  ih 
line  along  which  a  man  on  the  deck  of  the  sailing  vesseL  would  look. 


THE    EARTH   AS    A    PLANET. 


The  earth  is  not  an  exact  sphere,  for  the  diameter  at  the  equator 
is  7926%niles,  and  at  the  poles  7899.  This  difference  in  the  two 
diameters  is  due  to  a  slight  flattening  at  the  poles.  Such  a  slightly 
flattened  sphere  is  called  an  oblate  spheroid.  Compared  to  the 
earth  as  a  whole  this  flattening  is  so  slight  that  it  cannot  be  shown 
on  an  ordinary  globe.  « 

Summary.  —  The  earth  is  a  slightly  flattened  sphere,  or  oblate 
spheroid.  Its  curved  surface  can  be  seen  on  the  ocean  ;  eclipses  of 
the  moon  prove  that  it  is  a  sphere  ;  its  size  and  shape  have  been 
measured ;  and  the  distance  around  it  in  all  directions  is  known 

2.  Other  Spheres.  — The  earth  is  only  one  of  a  great  num- 
ber of  spheres  in  space.  The  nearest  of  these  is  the  moc 
whose  average  distance  is 
about  240,000  miles.  All 
the  stars  are  also  spheres, 
far  larger  than  the  moon, 
and  billions  of  miles  away. 
At  the  rate  of  an  express 
train  it  would  take  tens  of 
thousands  of  years  to  reach 
the  nearest  star.  These  stars 
are  all  flery  hot ;  but  the 
moon  is  a  cold  mass  of  rock. 

The  huge  sun,  another 
sphere,  is  a  star  w^ith  a  diam- 
eter of  860,000  miles  (Fig. 
7).  Its  average  distance 
from  the  earth  is  92,750,000 
miles,  and  yet  it  is  so  hot  that  heat  and  light  from  it  cross 
that  distance,  making  life  on  the  earth  possible. 

The  sun  is  the  center  of  a  family  of  spheres  which  form 
the  solar  system.  In  this  system  there  are  eight  large 
spheres  called  planets,  of  which  the  earth  is  one.  The  sun 
and  stars  shine  by  their  own  light ;  but  the  planets  merely 
reflect  sunlight,  as  the  moon  does.     The  bright  evening  and 


Fig.  7.  —  To  show  the  great  size  of  the 
sun.  The  earth,  moon,  and  orbit  of 
the  moon  could  all  be  placed  inside 
the  sun,  as  shown. 


NEW   PHYSICAL    GEOGRAPHY, 


morning  "  stars  "  are  planets,  like  the  earth.  From  one  of 
them  the  earth  would  be  seen  to  have  the  same  steady,  bright 
light  that  they  show  to  us. 


> 

O  3|-  to 

Ul  IU<  < 

z    S  >iu  S 


Q. 

13 


Z 

< 
CO 


3 
Z 
< 


Z 

H 
Q. 


2|-f^M^^ 


<0 


i  '-I'll.OOO.oO-J   1 

I        --93.0tK).000 


-er.odo.ooo 

-36,(KX),000 


■430^000^000 


•  -  -881jOOO^0O0 


---l,77a,QOO,OJO 


Fig.  8.  —  Ttie  distances  from  the  sun  to  the  different  planets. 

are  distances  in  miles. 


2,775,000.000--' 


The  figures 


EARTH 


Some  of  the  planets  are  far  more  distant  than  the  sun  (Fig.  8), 
Neptune,  the  most  distant  of  all,  being  over  2,700,000,000  miles. 
How  distant  that  is  may  perhaps  be  understood  by  the  following 

illustration.  If  an  express  train  could 
have  started  toward  Neptune  in  the 
time  of  Christ,  and  have  traveled 
steadily  onward  day  and  night  at 
the  rate  of  sixty  miles  an  hour,  it 
would  not  yet  be  halfway  there. 

Not  only  are  the  planets  far  away, 
but  some  of  them  are  very  large 
(Figs.  9,  10).  Jupiter,  the  largest, 
is  86,000  miles  in  diameter.  In  the 
space  between  Mars  and  Jupiter  there 
are  also  a  number  of  very  small 
spheres,  called  asteroids.  The  largest 
is  about  500  miles  in  diameter. 

Summary.  —  Other  spheres  besides 
the  earth  are  the  stars,  sun,  moon, 
planets,  and  asteroids.  TJie  moon 
and  p?awe^s  are  cold,  and  shine  by 
reflected  light ;  the  stars  and  sun  are 
fiery  hot.  In  the  solar  system,  7thich 
includes  the  S2in,  moon,  j^lanets,  and 
asteroids,  the  largest  sphere  is  the  sun, 
the  largest  planet  Jupiter,  and  the  most  distant  planet  Neptune. 


size 


Fig.  9.  —  To  show  the  relative 
of  the  four  smaller  planets. 
The  figures  are  diameters  in 
miles. 


THE  EARTH  AS  A   PLANET. 


Jupiter 


3.  Movements  of  the  Spheres.  —  Little  is  known  about  the 
motions  of  the  distant  stars.  But  all  the  planets  whose 
movements  are 
known  have  been 
found  to  turn,  or 
rotate^  on  an  axis. 
The  earth  takes 
one  day  for  rota- 
tion ;  the  sun  over 
25  days  ;  Jupiter 
9  hours,  55  min- 
utes ;  the  moon 
21^  days. 

All  members  of 
the     solar    system 

also    travel     or   Te-    ^^^-  lO-  —  '^^  show  the  relative  size  of  the  four  larger 
,  1      i  1  planets. 

volve^    around    the 

sun.  This  revolution^  is  along  a  nearly  circular  path,  or 
orhit.  The  orbit  is  not  an  exact  circle,  but  an  ellipse  (Fig. 
11),  and  the  sun,  instead  of  being  at  the  center,  is  a  little 
to   one  side,  at  one  of  t\\Q  foci  of  the  ellipse.     This  causes 

the  earth  to  be 
nearer  the  sun 
at  one  season 
(over  91,000,000 
miles)  than  in  the 
opposite  (over 
94,000,000  miles), 
when  it  reaches 
the  other  end  of 
the  ellipse.  The 
earth  requires  a 
little  over  365  days,  or  one  year,  to  make  a  complete  revo- 
lution around  the  sun. 

1  For  fuller  treatment  of  revolution,  see  Appendix  A 


Fig.  11.  —  A  circle  (on  left)  and  ellipse  (on  right). 
Find  the  center  of  the  circle  (C)  and  the  foci  of 
the  ellipse  (Fi^). 


6  NEIV  PHYSICAL   GEOGRAPHY. 

Mercury,  the  smallest  and  nearest  of  the  planets  (Figs.  8,  9), 
requires  only  88  days  for  a  single  revolution.  What  is  the  time 
required  by  the  other  planets  (Fig.  12)  ? 

Several  of  the  planets  have  moons.  The  word  satellite.^  mean- 
ing follower,  is  given 
to  these  smaller 
spheres  because  they 
follow  their  planets 
in  their  revolution 
dround  the  sun.  The 
earth  has  one  moon ; 
no  moons  have  been 
discovered  for  Mer- 
cury or  Venus ;  but 
Saturn  has  eight.  It 
is  believed  that  each 


Fig.   12.  —  Time  of  revolution  of  the  planets. 


satellite  rotates  on  an  axis  and  revolves  in  an  ellipse  around  its 
planet.  The  moon  makes  one  revolution  around  the  earth  in 
about  27|-  days. 

Summary.  —  So  far  as  known,  all  the  planets  rotate  07i  axes,  and 
all  revolve  aromid  the  sun  in  elliiitical  orbits.  The  jjeriods  of  rota- 
tion  and  revolution  differ.  Satellites  accompany  several  of  the 
planets. 

4.  Rotation  of  the  Earth.  —  Many  uninformed  people  believe 
that  the  sun  rises,  passes  through  the  heavens,  and  sets  in 
the  west.  Our  own  ancestors,  centuries  ago,  held  the  same 
belief.  We  still  use  their  terms,  sunrise  and  sunset.,  though 
we  well  know  that  it  is  the  turning  of  the  earth  on  its  axis 
that  makes  the  sun  appear  to  rise  and  set.  In  looking  from 
the  window  of  a  train  it  sometimes  seems  as  if  objects  were 
passing  by,  while  it  is  really  you  yourself  that  is  moving. 
In  the  same  way,  as  the  earth  turns  with  us  toward  the  east, 
the  sun  seems  to  travel  in  the  opposite  direction. 

The  rising  and  setting  of  the  moon,  and  the  apparent  move- 
ments of  the  stars  at  night,  are  also  due  to  the  earth's  rotation. 


THE  EARTH  AS  A   PLANET,  7 

Find  the  North  Star  by  following  the  pointers  on  the  outer  side  of 

the  Great  Dipper  (Fig.  13).     Notice  that  it  does  not  move  at  night, 

but   that   the  Dipper  and  other  stars  seem  to  swing  around  it. 

The  farther  a  star  is  from  the  North  Star  the  greater  the  circle 

through  which  it  swings,  those  far 

away  rising  in  the  east  and  setting  North  star* 

in  the  west.     It  used  to  be  thought 

that   the    sky    was    a  great   dome 

with  stars   set  in  it,  a  few   miles 

from  the  earth,  and  that  it  slowly 

swung    around    the     earth.       We 

now   know   that   the    earth's    axis  ^* 

points  toward  the  North  Star  and 

that,,  as  the  earth  turns,  it  causes    er-''-^%^^ 

the  stars  to  appear  to  swing  round  "^'^^,^ % 

the  North  Star.  V  / 

Summary.  —  It     was    formerly  * *' 

niouqht  that  the  sun,  moon,  and  stars     ^'^-  ^^'  -^,\^Z^^  ^^^i''"  ^°^ 
^  '  ^  North  Star. 

moved;    we   now   know    that    these 

apparent  movements  are  caused  by  the  earth^s  rotation.  The  axis 
of  the  earth  points  toivai'd  the  North  Star;  therefore  the  other  stars 
seem  to  circle  round  it. 

5.  Effects  of  Revolution  and  Rotation.  — Rotation  of  the 
earth  has  given  the  basis  for  our  computation  of  time.  Thus 
we  reckon  a  day  as  the  period  required  for  one  rotation 
(24  hours).  The  day  is  divided  into  hours,  each  hour  being 
the  time  required  for  the  sun's  rays  to  advance  15^  over  the 
curved  surface  of  the  rotating  earth.  By  rotation,  also,  the 
day  is  divided  into  a  period  of  light  and  one  of  darkness. 
Name  some  habits  of  plants,  animals,  and  men  that  are  de- 
termined by  this  effect  of  rotation. 

Revolution  of  the  earth  is  also  a  matter  of  the  highest 
importance.  By  it  another  standard  of  time,  the  year,  is 
fixed.  Revolution  also  causes  an  apparent  movement  of 
the  sun,  by  which  it  rises  and  sets  farther  north  or  south 
at  different  times.     These   changes   in   the  sun's   position. 


8  NEW  PHYSICAL   GEOGRAPHY, 

which  cause  the  seasons,  have  determined  some  of  man's 
most  characteristic  habits.  Name  some  ways  in  which  revo- 
lution affects  you, — your  home,  clothes,  foods,  and  games. 
Recall  from  your  study  of  geography  how  revolution  affects 
the  habits  of  the  Eskimos. 

Summary.  —  Rotation  determines  the  length  of  our  day,  causes 
day  and  night,  and  influences  our  habits.  Revolution  gives  us  our 
year,  our  seasons,  and  also  profoundly  affects  our  habits. 

6.  Gravity  and  Gravitation.  —  The  earth  exerts  on  all 
bodies  upon  it  an  attraction  which  we  call  gravity.  By 
gravity  men  are  held  to  the  surface  of  the  earth ;  a  stone 
thrown  into  the  air  is  drawn  back  to  the  earth;  the  air  is 
prevented  from  flying  away  into  space;  and  the  oceans  are 
held  in  place.  It  gives  to  the  ocean  a  curved  surface,  be- 
cause each  particle  of  water  is  attracted  toward  the  center 
of  the  sphere.  Each  part  of  this  curved  surface,  or  sea 
levels  is  at  right  angles  to  a  line  leading  toward  the  earth's 
''  ^nter. 

Bodies  in  space  also  exert  an  attraction  on  other  spheres. 
For  example,  the  moon  exerts  an  attraction  upon  the  earth, 
and  the  earth  upon  the  moon;  but  the  earth,  being  larger, 
has  the  stronger  effect.  This  attraction  of  bodies  in  space 
is  called  the  attraction  of  gravitation. 

Gravitation  is  the  bond  that  holds  the  earth  and  other 
planets  to  the  orbits  along  which  they  travel  about  the  sun. 
If  it  could  be  possible  for  the  sun  to  lose  its  attraction  of 
gravitation,  the  earth  would  fly  off  into  space,  as  a  stone 
whirled  by  a  string  flies  away  if  the  string  breaks.  Gravita- 
tion also  holds  the  moon  so  firmly  that  it  swings  around  the 
earth  with  such  regularity  that  its  position  a  thousand  years 
from  now  can  be  accurately  foretold.  The  law  of  gravita- 
tion was  discovered  over  two  centuries  ago  by  Sir  Isaac 
Newton;  yet  even  now  no  one  knows  exactly  what  causes 
it  nor  why  it  operates  in  the  universe. 


THE  EARTH  AS  A   PLANET, 


held  by  gravitation,  the  earth  is  able  to  travel  along  its  orbit  of 
600,000,000  miles  each  year  at  a  rate  of  over  1000  miles  a  minute. 
At  the  same  time,  it  is  whirling  on  its  axis  so  rapidly  that  a  per- 
son on  the  equator  is  moving  at  the  rate  of  17  miles  a  minute.  We 
are  not  aware  of  these  rapid  movements,  because  the  land,  water, 
and  air  go  with  us.  Even  when  traveling  on  a  noisy  railw^ay 
train,  we  sometimes  forget  that  we  are  moving.  But  the  earth 
moves  without  jar  or  noise,  and  there  are  no  near-by  objects  for 
us  to  swiftly  pass ; 
therefore,  for  many 
generations  men  did 
not  even  suspect  that 
they  were  moving  at 
all. 

Summary.  —  Grav- 
ity is  the  attraction 
that  holds  objects  to 
the  earth',  it  causes 
the  curved  sxtrface 
called  sea  level. 
Gravitation,  discov- 
ered hy  Newton,  is 
the  attraction  exerted 
on  one  another  hy 
bodies  in  space  and 
by  which  the  spheres 
are  held  to  their  orbits. 

7.  Heat  in  the 
oolar  System. — 

The  sun  is  the  only 

member  of  the  solar 

system  that  is  hot 

enough    to    glow  ; 

but  in  past  ages  the  other  members  have  apparently  also  been 

hot.     Jupiter  appears  still   to   be    so  warm  at   the    surface 

that  the  water  rises  in  clouds  of  steam.     The  earth  is  cold 


seeming  to   iiidi- 


FiG.    li.  —  Craters   ou   the   moon 

cats  former  volcanic  eruptions  due  to  a  heated 
condition  of  the  interior. 


10 


NEW  PHYSICAL   GEOGRAPHY, 


at   the    surface,  but   hot  within  (p.  17) ;    the  small  moon, 
though  now  cold,  was  apparently  once  hot  within. 

The  heat  of  the  sun  is  so  great  that  even  mineral  substances 
exist  in  the  form  of  gases.  This  white  hot  sun  is  slowly  cool- 
ing by  radiating  its 
heat  off  into  space; 
but  a  few  small 
points,  of  which  the 
earth  is  one  (Fig. 
15),  intercept  a 
minute  portion  of 
these  rays,  on  which 
|*Y\^\^  -  animal     and    plant 

Fig.   15.  — To  illustrate  the  very  small  proportion  of    ^^^^    Clepencl. 

all  the  rays  passing  out  from  the  sun  that  reach  'iv'fl^  ■(-  A 

the  earth.  With   great   speed 

these  rays  cross  the 
93,000,000  miles  that  separate  us  from  the  smi.  They  reach  the 
earth  in  about  8  minutes,  while^  at  the  rate  of  a  fast  express 
train,  175  years  would  be  required.  The  distant  planet  Neptune 
doubtless  receives  too  little  heat  for  life ;  Mercury  is  so  near 
that  it  perhaps  receives  too  much ;  but  the  earth  is  so  favorably 
situated  that  it  receives  neither  too  much  nor  too  little.  As 
the  sun  cools  down  to  a  red  heat,  in  some  far-distant  future  age, 
life  on  the  earth  will  no  longer  be  possible. 

Summary.  —  TJie   members   of  the   solar  system  shotv   signs   of 
heat,  either  past  or  present.     Heat,  radiated  from  the  ivhite  hot  sun, 
passes  rapidly  across  space  ;  ayid  some   of  it,  reaching   the  earth, 
makes  life  possible. 


TOPIOAL   OUTUNK,    QUKSTIONS,    AND   SUGQKSTIONB. 

Topical  Outline.  —  1.   Shape  of  Earth.  —  Former  belief ;  proofs  of 
roundness ;  exact  shape ;  length  of  diameters. 

2.  Other   Spheres.  —  The    moon;  stars;  sun;  solar   system;  relative 
Ze  of  planets;  relative  distance  ;  asteroids. 

3.  Movements  of  the  Spheres.  —  (a)  Rotation :  time  required,    (h)  Revo- 


THE  EARTH  AS  A   PLANET.  XI 

lution :  nature  of  path :  effect  on  distance  from  sun  ./O  earth  ;  time  re 
quired,     (c)  Satellites  :  meaning  of  nanv  ,  number ;  movements. 

4.  Rotation  of  the  Earth.  —  Apparen*  novement  of  sun,  former  belief ; 
real  explanation  ;  movements  of  stars     explanation 

5.  Effects  of  Rotation  and  Revolut  on.  —  (.r)  Rotation  :  effect  on  divi- 
sions of  time;  on  day  and  night;  m  L  ibits  of  man,  (h)  Revolution: 
effect  on  division  of  time  ;  on  seasons:  on  habits  of  man. 

6.  Gravity  and  Gravitation. —  (a>  ^Sravity  :  nature;  effects;  nature  of 
sea  level,  (b)  Gravitation  :  nature :  movements  of  moon  and  planets ; 
discovery  by  Newton,     (c)  RaDid  movements  of  earth. 

7.  Heat  in  the  Solar  System,  —(a)  Evidence  of  heat  in  the  solar  sys- 
tem, (b)  Sun's  heat:  condition  of  sun;  rate  of  passage  of  rays;  pro- 
portion received  by  earth  ;  other  planets  ;  effect  of  future  cooling  of  sun. 

Questions.  —  Section  1  What  was  formerly  believed  concerning  the 
shape  of  the  earth?  What  proof  is  there  that  the  earth  is  spherical? 
What  is  its  exact  shape  ?     Give  its  two  diameters. 

2.  What  other  kinds  of  spheres  are  there  ?  How  do  planets  and  stars 
differ?  What  is  the  solar  system  ?  What  are  asteroids  ?  Give  the  dis- 
tance from  the  sun  to  each  of  the  planets  (Fig.  8).  Name  the  planets 
in  the  order  of  their  size  (Figs.  9  and  10). 

3.  What  important  movements  have  the  planets  ?  State  the  differ- 
ence in  time  of  rotation.  Of  revolution.  What  is  the  distance  from 
earth  to  sun  at  opposite  seasons?  Why  this  difference  ?  Give  some  facts 
about  satellites. 

4.  AVhat  was  formerly  thought  regarding  the  daily  rr.ovement  of  the 
sun  ?  What  is  now^  known  to  be  the  cause  of  it  ?  Describe  the  move- 
ment of  the  stars,  and  explain  them. 

5.  W" hat  are  the  important  effects  of  rotation?     CI  revolution ? 

6.  W^hat  is  gravity  ?  Give  examples  of  its  effects.  W^hat  is  the 
attraction  of  gravitation  ?  What  effect  has  this  upon  revolution?  Why 
are  the  earth's  movements  not  more  noticeable 

7.  What  is  the  evidence  of  heat  in  the  memib<^rs  of  the  solar  system? 
What  change  is  going  on   in   the  sun?     Whflu  effect  has  that  on   the 
earth?     Why  is  there  probably  no  life  on  N.i^oune  or  Mercury?     At 
vhat  rate  does  sunligQt  travel  ? 

Suggestions-  — ■  These  sugges/ions  are  mad6  rather  freely,  though  it  is  not 
expected  that  any  school  iv  ill  find  it  feasible  to-^f-rry  out  all,  or  even  a  majority. 
From  among  them,  however,  every  teacher  tviU  find  it  possible  to  select  some. 
(1)  Carefully  examine  the  moon  and  n^rfce  its  roundness.  If  possible, 
look  for  the  craters  through  ^,  telescope  or  spyglass.  (2)  If  an  eclipse  of 
the  moon  comes  during  thp  year,  observe  it  and  note  the  circular  outline 
of  the  earth's  shadow.     (3)  With  a  lamp,  throw  on  the  wall  the  shadow 


12  NJEW  PHYSICAL   GEOGRAPHY. 

of  a  ball  in  various  positions.  Do  the  same  with  a  cylinder ;  with  a 
square.  Which  always  shows  one  kind  of  outline  ?  (4)  A  period  devoted 
to  the  meaning  of  scale  may  be  combined  with  a  study  of  the  size  and  dis- 
tance of  the  members  of  the  solar  system.  This  can  be  done  with  profit 
by  cutting  disks  out  of  brown  paper  to  represent  the  planets  (say  on  a 
scale  of  one  inch  for  5000  miles)  ;  and  marking  off  distances  in  the  school 
yard  (say  on  a  scale  of  one  inch  for  200,000  miles)  to  represent  distances. 

(5)  Take  a  string  five  feet  long  with  a  loop  in  the  end.  Put  the  loop  over 
a  nail  driven  in  the  floor.  With  a  piece  of  chalk  at  the  other  end  of  the 
string  draw  a  circle.  Now  drive  another  nail  two  inches  from  the  first. 
Take  a  string  ten  feet  long  and  tie  the  ends.  Put  it  over  the  two  nails, 
and  with  chalk  held  in  the  loop  draw  a  figure  as  near  a  circle  as  you 
can.  It  will  not  be  a  circle,  but  an  ellipse.  If  you  put  the  two  nails  (the 
foci)  farther  apart,  say  six  inches,  the  ellipse  will  be  still  less  like  a  circle. 

(6)  Rotate  a  globe  or  apple  in  front  of  a  light  to  understand  the  cause 
of  day  and  night.  (7)  Observe  the  stars  of  the  Great  Dipper  and  the 
North  Star  at  8,  9,  and  10  o'clock.  What  changes  do  you  notice  ? 
(8)  Compare  the  movements  of  a  planet  in  the  heavens,  say  the  evening 
"  star,"  with  that  of  a  neighboring  star.  Why  the  difference  ?  (9)  With 
a  telescope  look  for  the  moons  of  Jupiter  and  the  rings  of  Saturn. 
(10)  What  are  shooting  stars  and  comets?  (11)  In  some  astronomy, 
read  about  the  sun  and  the  planets.  (12)  Find  out  what  Aristotle, 
Magellan,  and  Galileo  learned  about  the  earth. 

Reference  Books.  —  References  to  a  few  selected  hooks  are  placed  at  the 
end  of  each  chapter.  Other  reference  hooks  and  magazines  are  listed  m 
Appendix  L.  Newcomb,  Elements  of  Astronomy^  American  Book  Co., 
New  York,  1900,  ^1.00 ;  Young,  Manual  of  Astronomy,  Ginn  &  Co., 
Boston,  1902,  $2.45;  Todd,  New  Astronomy,  American  Book  Co.,  New 
York,  1897,^1.30;  Lockyer,  The  Chemistry  of  the  Su7i,  Macmillan  Co., 
New  York,  1887,  ^4.50. 


CHAPTER  IT. 


GENERAL  FEATURES  OF  THE  EARTH.  1 


There  are  three  quite 
different  parts  of  tlie 
earth :  (1)  the  solid 
earth ;  (2)  the  liquid 
ocean  which  partially 
covers  the  solid  earth ; 
and  (3)  the  gaseous 
envelope,  or  atmosphere. 

8.  The  Atmosphere. 2 
—  There  is  some  air  at 
a  height  of  200  or  300 
miles  from  the  earth ; 
but  most  of  it  is  with- 
in a  few  miles  of  the 
surface.  The  air  is  a 
mixture  of  transparent 
gases,  mainly  oxygen 
and  nitrogen,  whose 
presence  on  every  hand  we  hardly  real- 
every  breath  draws  it  in  for  the  pur- 
ing  life-giving  oxygen.  Though  it 
we  feel  its  presence  when  the  wind 
moving  rapidly  through  it. 


A 


w^^    ^*  1.*  •■» 


Fig.  16.  —  Rela- 
water  on  the 
refer  to  miles, 
miles  being 
ocean  depths. 


to 

Q 
< 

a: 
O 

10 
0) 

to 


tive  depth  of  air  and 
earth.  The  figures 
five  and  one  half 
one  of  the  greatest 


ize.  Yet  our 
pose  of  supply- 
cannot  be  seen, 
blows,  or  when 


There  are  many  ways  in  which  the  air  is  of  high  importance. 
All  plants  and  animals  depend  upon  its  gases  for  life.     Its  oxygen 


1  For  latitude  and  longitude,  see  Appendix  B  ;  for  maps,  see  Appendix  I. 

2  See  also  Chapter  XII. 

13 


*14  NEW  I'HYSICAL   GEOGRAPHY, 

causes  fire  to  burn,  and,  by  a  slow  combustion,  causes  decay  of 
animal  and  plant  tissues.  It  diffuses  light  and  heat  from  the 
sun,  and  transmits  the  sound  waves  upon  which  hearing  depends. 
Winds,  which  bear  vapor  and  warm  and  cold  air  from  place  to 
place,  are  a  result  of  its  movement.  For  many  centuries  the  wind 
has  been  used  for  driving  ships  through  the  water  and  for  turn- 
ing windmills  on  the  land. 

The  surface  of  the  earth  itself  is  profoundly  modified  by  the 
influence  of  the  air.  Winds  move  loose  fragments  about  and 
wear  the  rocks  away,  especially  in  desert  regions.  Eains,  made 
possible  by  vapor  in  the  air,  give  rise  to  streams,  which  carve 
channels  in  the  land  and  bear  rock  fragments  to  the  sea.  Waves, 
which  winds  form  in  the  ocean,  batter  at  the  rocky  seacoast. 
Even  quiet  air,  by  the  action  of  its  water  vapor  and  oxygen,  is 
causing  the  solid  rock  to  slowly  decay  and  crumble.  This  forms 
the  soil  upon  which  so  many  plants  depend  for  food. 

Summary.  —  Hie  air,  composed  chiefly  of  oxygen  and  nitrogen, 
extends  200  or  300  miles  above  the  earth,  hut  Is  mainly  near  the  sur- 
face. Breathing,  fire,  decay,  diffusion  of  light  and  heat,  hearing, 
winds,  rain,  toaves,  and  many  changes  of  the  land,  includijig  the 
formation  of  soil,  are  dependent  on  the  atmosphere. 

9.  The  Oceans.^  —  If  the  earth  were  a  perfect  sphere,  it 
would  be  entirely  covered  by  water  to  a  depth  of  several 
thousand  feet ;  but  the  surface  is  so  irregular  that  the  ocean 
is  not  able  to  completely  cover  it,  as  the  air  does.  It  has 
been  drawn  by  gravity  into  the  depressions  and  rises  high 
enough  to  cover  only  the  continent  margins  (Fig.  316). 

Nearly  three  fourths  of  the  solid  earth  is  hidden  from 
view  by  this  water  mantle,  the  area  of  the  oceans  being 
about  145,000,000  square  miles,  of  the  lands  about  52,000,000 
square  miles.  Near  their  contact  with  the  continents  the 
oceans  are  shallow ;  but  far  from  land  the  wa^er  is  deep. 
One  may  sail,  with  no  land  in  sight,  for  thousaridf^  of  miles 
in  water  whose  average  depth  is  10,000  to  15,000  Toet.     In 

1  See  also  Chapter  X. 


GENERAL  FEATURES   OF  THE  EARTH.  15 

its  deepest  parts  the  ocean  has  a  depth  of  over  five  and  a 
half  miles. 

This  vast  expanse  of  water  is  of  great  importance  in  many 
ways.  It  is  the  seat  of  abundant  life,  many  forms  of  which 
are  of  such  value  that  ships  are  sent  out  to  secure  them. 
Cod,  halibut,  haddock,  bluefish,  salmon,  shad,  lobsters,  oysters, 
clams,  seals,  whales,  sponges,  pearl  oysters,  and  precious  corals 
are  among  the  ocean  animals  of  importance  to  man. 

For  a  long  time  the  ocean  was  an  almost  impassable  barrier  to 
the  spread  of  man ;  but  as  men  learned  to  navigate  and  to  build 
strong  ships,  it  became  a  highway  instead  of  a  barrier.  To-day 
the  Atlantic  is  crossed  with  speed  and  comfort  in  iive  or  six 
days ;  less  than  a  century  ago  this  journey  required  weeks  and 
was  one  of  peril.  To-day  communication  between  America  and 
Europe  is  easier  than  between  Rome  and  Athens  at  the  time  of 
the  Roman  Empire.  Ships  now  cross  the  oceans  in  all  directions, 
carrying  merchandise  and  passengers  to  every  quarter  of  the 
globe.  The  harbors  from  which  these  ships  go  forth  have  be- 
come the  seats  of  great  cities,  prospering  by  their  commerce  a,nd 
by  the  industries  to  which  it  gives  rise.  By  means  of  the 
ocean  highway,  too,  civilization  has  rapidly  spread  to  all  quarters 
of  the  globe. 

It  is  the  ocean  that  supplies  the  vapor  for  rain,  upon  which  all 
land  animals  and  plants  depend.  The  ocean  also  profoundly  in- 
fluences the  temperature  of  neighboring  lands,  moderating  the 
heat  of  summer  and  the  cold  of  winter.  Therefore,  lands  reached 
by  ocean  winds,  like  the  northwestern  coast  of  United  States  and 
Europe,  have  far  less  extreme  climates  than  lands  in  the  same 
latitude,  like  central  and  eastern  United  States,  where  ocean  winds 
are  less  common. 

Summary.  —  TJie  ocean  occupies  depressions  on  the  eartWs  sur- 
face, covering  three  fourths  of  the  globe  to  an  average  depth  of 
10,000  to  15,000  feet.  The  ocean  is  of  importaiice  as  a  source 
of  food-fishes  and  other  valuable  animals;  as  the  seat  of  ex- 
tensive navigation;  as  the  source  of  vaj^or;  and  in  modifying 
climate. 


16 


NEW  PHYSICAL   GEOGRAPHY, 


10.  The  Solid  Earth.  —  Near  the  continents  the  sea  floor  is 
covered  with  sediment  washed  from  the  land  by  rain,  rivers, 
and  waves.  Farther  out,  it  is  mantled  with  the  remains  of 
animals  that,  on  dying,  have  settled  from  the  water  above. 
Almost  everywhere  on  the  dry  land  there  is  a  layer  of  loose 
rock  fragments,  the  surface  part  of  which  is  called  soil.  Thus 
nearly  the  entire  earth  is  covered  by  loose  materials. 

In  some  places  the  soil  has  been  brought  by  glaciers,  in 
others  by  rivers;  but  most  of  it  has  been  formed  by  the  de- 
cay and  crumbling  of  the  rocks.     Were  it  not  for  this  soil 

most  of  the  plants, 
which  are  of  such 
use  in  supplying 
materials  for  food, 
clothing,  and  shel- 
ter, could  not 
grow.  The  soil 
offers  a  chance  for 
the  roots  to  pene- 
trate,  seeking  wa- 
ter and  plant  food, 
and  also  holding 
the  plants  up- 
right. 

Wherever  the 
soil  mantle  is  penetrated  to  great  enough  depth,  solid  rock  is 
found  beneath  it  (Fig.  17).  Sometimes  the  rock  is  several  hun- 
dred feet  beneath  the  surface;  but  it  is  usually  found  at  a 
depth  of  a  few  feet  or  a  score  or  two  of  feet.  In  places,  espe- 
cially among  mountains  or  on  other  steep  slopes,  there  is  no 
soil-cover  at  all.  As  the  rock  decays  in  such  situations,  the 
fragments  fall  away  so  quickly  that  soil  cannot  accumulate. 

The  rock  that  is  everywhere  found  beneath  the  soil  varies 
greatly  from  place  to  place,  often  consisting  of  materials 
which  are  of  great  use  to  man.     In  some  places  it  is  sand- 


FiG.  17.  —Rock  beneath  the  soil. 


QEN^RAL  VEATUItt:S  OF  THE  FAUTB, 


17 


/vrmospHEf^E 


stone  or  granite,  useful  for  building  purposes  ;  in  other  places 
it  is  limestone,  valuable  for  building,  for  making  lime,  or  for 
use  in  blast  furnaces.  In  various  parts  of  the  world,  layers  of 
coal  are  found  bedded  with  the 
rocks ;  and  there  are  deposits 
of  iron  ore,  salt,  and  other  sub- 
stances ;  also  veins  of  lead,  zinc, 
silver,  gold,  and  other  metals. 

Summary.  —  The  solid  earth,  like 
the  air  and  ocean,  is  of  great  im- 
portance to  man.  It  furnishes  him 
ivith  a  home  ;  it  is  almost  every- 
where covered  ivith  a  soil  mantle, 
in  ivhich  food  and  other  plants 
grow  ;  everywhere  beneath  the  soil 
mantle  is  found  solid  rock,  from 
which  many  valuable  mineral  sub- 
stances are  obtained. 

11.  The  Earth's  Interior.  — 
From  river  valleys,  tunnels, 
quarries,  mines,  and  well  bor- 
ings many  facts  have  been 
learned  about  the  outer  part 
of  the  solid  earth.  But  this 
knowledge  tells  little  about 
the  great  interior.  However, 
astronomers  have  shown  that, 
while  the  outer  part  of  the 
earth  is  from  2  to  3  times  as 
heavy  as  water,  the  interior  is 
6  to  10  times  as  heavy.  It  is 
perhaps  made  of  metal. 

Several  facts  indicate  that  the  interior  is  highly  heated : 
there  are  hot  springs ;  volcanoes  erupt  melted  rock ;  and 
mines  show  an  increase  in  temperature  of  1°  for  every  50 

Q 


Fig.  18.  —  To  show  the  relative  thick- 
ness of  the  air  and  solid  earth. 


18  NEW  PHYSICAL   GEOGRAPET. 

or  60  feet  of  descent.  If  this  increase  continues,  tlie  melt- 
ing point  of  rocks  must  be  reached  at  no  great  depth. 

It  was  formerly  believed  that  beneath  a  thin  outer  crust 
the  interior  was  molten ;  but  it  is  now  considered  certain 
that,  though  very  hoi,  the  interior  is  solid.  We  still  use  the 
term  earth's  crust,  however,  for  the  cold  outer  portion  of  the 
earth.  There  are  a  number  of  reasons  for  the  belief  that 
the  interior  is  solid :  (1)  if  it  were  liquid  there  would  be 
tides  in  it ;  (2)  the  behavior  of  the  earth  toward  other 
spheres  is  that  of  a  solid  body ;  (3)  earthquake  shocks  in 
Japan  have  been  measured  by  delicate  instruments  in  Eng- 
land, and  the  time  of  passage  indicates  a  solid  interior. 

It  is  a  well-known  fact  that  greater  heat  is  required  to 
melt  most  substances  under  pressure  than  without  pressure. 
It  is  believed,  therefore,  that  the  interior  of  the  earth  is  pre- 
vented from  melting  by  the  tremendous  weight,  or  pressure, 
of  the  rocks  that  rest  upon  it.  At  a  depth  of  six  miles 
the  pressure  is  great  enough  to  crush  rocks ;  and,  therefore, 
deep  in  the  earth,  below  this  upper  portion,  or  zone  of  fracture, 
cavities  cannot  exist. 

The  interior  heat  is  one  of  the  arguments  in  favor  of  the  belief 
that  the  earth  was  once  a  still  hotter  body  (p.  9),  probably  part 
of  a  nebula,  from  which  the  sun,  earth,  moon,  and  the  other  mem- 
bers of  the  solar  system  have  descended.  The  earth  is  still  losing 
heat;  but  it  is  so  large  that  many  ages  more  will  be  required  to 
make  it  completely  cold,  like  the  smaller  moon. 

Summary.  —  Several  facts  indicate  that  the  interior  of  the  earth  is 
highly  heated,  and  it  ivas  formerly  thought  to  he  molten  ;  hut,  for  a 
number  of  reasons,  it  is  now  believed  to  he  solid,  though  hot,  being 
prevented  from  melting  by  the  pressure  upon  it. 

12.  Air,  Water,  and  Rock.  —  At  ordinary  temperatures  the 
air  is  a  mixture  of  gases ;  but  with  great  cold  and  pressure 
these  gases  may  be  changed  to  a  liquid  and  even  to  a  solid 
state.     Water,  ordinarily  a  liquid,  changes  at  32°  to  a  solid- 


GENERAL  FEATURES   OF  THE  EARTH.  19 

and  at  212°  to  a  gas;  in  fact,  some  water- vapor  gas  rises  from 
water  at  ordinary  temperatures.  Rock,  as  we  know  it,  is  a 
solid;  but  volcanoes  show  that  under  higher  temperatures  it 
becomes  a  liquid;  and  in  the  very  hot  sun,  some  of  the  rock 
elements  are  so  hot  that  they  are  in  the  state  of  gases. 
From  this  it  is  seen  that  the  terms  gas^  liquid^  and  solid 
apply  merely  to  states  of  matter.  When  the  conditions 
change,  any  one  of  these  states  of  matter  may  be  altered  to 
one  of  the  other  states. 

The  three  earth  materials  —  air,  water,  and  rock  —  have  been 
spoken  of  as  if  they  were  quite  separate ;  but  really  they  are 
closely  related  and  mingled.  There  is  not  much  rock  material  in 
the  atmosphere,  though  volcanic  dust  is  often  borne  long  distances 
in  it ;  and  the  haziness  of  the  air  is  partly  due  to  dust  blown  up 
from  the  ground.  Water  vapor  is  mixed  with  all  air,  even  that 
of  the  driest  deserts. 

Water  also  pervades  the  earth's  crust,  entering  even  the  densest 
rocks.  Wells  reach  it  and  supply  drinking  water ;  it  slowly  oozes 
from  the  ground  in  springs  ;  miuers  find  it  far  below  the  surface  ; 
and  volcanic  eruptions  bring  vast  quantities  of  it  to  the  surface. 
In  cold  climates  it  is  frozen,  changing  the  soil  to  a  solid,  rocklike 
mass.  In  northern  Siberia  the  ground  is  permanently  frozen  to 
a  depth  of  several  hundred  feet.  That  air  also  enters  the  ground 
is  proved  by  the  fact  that  many  plants  die  for  lack  of  it  when 
their  roots  are  submerged. 

Air  is  also  mixed  with  water.     If  a  fish  is  placed  in  water 

from  which  the  air  has  been  expelled,  it  will  die  because  there  is 

.no  oxygen  for  it  to  breathe.     All  water,  on  the  land  or  in  the  sea, 

bears  mineral  substances  in  solution;  and  rock  fragments  min- 

grled  in  suspension  are  also  present  in  water. 

Summary. — Air  (gas),  ruater  (liquid),  and  rock  (solid)  may  each 
oe  changed  to  one  of  the  other  states  of  matter.  Tliey  are  mingled: 
there  is  earth  material  and  water  vapor  in  the  air ;  air  and  water  in 
the  earth;  and  air  and  rock  material  in  the  water. 

13.  Irregularities  of  the  Earth's  Crust.  —  While  the  earth 
is  a  huge  sphere  flattened  at  the  poles,  its  outline  is  far  from 


20 


NEW  PHYSICAL   GEOGEAPHT. 


80,000  FT. 


20,000  FT. 


10,000  FT. 
SEA  LEVEL 


-10,000  FT. 


CO,  000  FT. 


80,000  FT. 

Fig.  19.  —  To  show  the  proportion  of  continents  and 
ocean  basins  between  different  levels. 


regular.  Its  surface  is  roughened  by  a  series  of  continent 
elevations,  between  which  are  broad  depressions,  occupied  by 
the  oceans.  The  ocean  depressions  average  10,000  to  15,000 
feet  in  depth;  but  the  average  height  of  the  lands  above  sea 
level  is  only  2000  to  3000  feet.     Fully  three  fourths  of  the 

ocean  bottoms  are 
broad  expanses  of 
plain;  and  much 
more  than  half 
the  land  is  either 
plain  or  plateau 
(Figs.  19,  21). 

Mountain 
chains  and  volca- 
noes rise  high 
above  the  general 
level  of  both  sea  bottom  and  land.  The  Hawaiian  Islands 
are  volcanic  cones  on  a  submarine  mountain  fold  fully  1500 
miles  in  length  ;  and  the  Japanese  Islands,  Philippines,  and 
West  Indies  are  also  mountain  chains  rising  from  the  sea  floor. 
It  is  among  the  mountain  chains  of  the  land  that  the  great- 
est elevations  on  the  globe  are  found.  In  the  Andes  there 
are  peaks  that  are  over  40,000  feet  above  the  sea  bottom  75 
miles  to  the  west.  The  highest  mountain  in  the  world.  Mount 
Everest,  is  about  5^  miles  high  ;  and  the  greatest  ocean  depth 
is  about  the  same  distance  beneath  the  sea.  Eleven  miles  is 
a  great  height  as  we  look  at  it  ;  but  it  is  a  very  small  amount 
compared  to  7900  miles,  the  diameter  of  the  earth. 

These  irregularities  of  the  earth's  surface  are  generally  believed 
to  result  from  the  heated  condition  of  the  interior  (p.  9).  As 
the  earth  cools  and  shrinks,  its  crust  wrinkles,  causing  some 
parts  to  rise,  others  to  settle  (p.  35^.  Such  changes  of  level 
are  even  now  in  progress  (p.  36),  and  there  are  many  proofs 
that  they  have  caused  great  change  in  the  past.  One  of  the 
most  important  facts  in  physical  geography  is  that  the  earth's 


GENERAL  FEATURES   OF  THE  EARTH,         '         21 

crust  is  in  slow  movement ;    for  by  reason  of  it,  the  outlines  of 
the  lands  and  oceans  are  ever  varying. 

Summary.  —  Tlie  earth's  surface  has  been  roughened  by  the  effects 
of  shrinking  of  the  heated  interior.  This  has  caused  continent  eleva- 
tions and  ocean  depressions,  and,  on  both  of  these,  mountain  chains 
and  volcanoes.  The  average  depth  of  the  ocean  is  about  five  times 
the  average  height  of  the  land  ;  but  the  loftiest  mountains  are  about 
as  high  as  the  greatest  ocean  depths j  making  a  total  difference  in 
level  of  about  eleven  miles. 

14.  Conflict  of  Erosion  and  Elevation.  —  Wherever  land  is 
exposed  to  the  air,  it  is  being  attacked  and  slowly  worn  away. 
The  weather  causes  the  rocks  to  slowly  crumble  (p.  38); 
rivers  carve  valleys  and  carry  the  rock  fragments  off  toward 
the  sea  (p.  52);  glaciers  scour  the  land  over  which  they 
pass  (p.  153)  ;  waves  batter  the  shore,  cutting  cliffs,  build- 
ing beaches,  and  supplying  rock  fragments  for  removal  by  the 
currents  (p.  210).  The  result  of  the  work  of  these  agencies 
of  erosion  is  that  the  land  surface  is  made  very  irregular. 

The  sea  floor,  on  the  other  hand,  is  made  more  regular. 
Beyond  the  reach  of  the  waves  there  is  practically  no  erosion  ; 
but  the  deposit  of  rock  fragments  from  the  land  is  leveling 
the  sea  bottom. 

Thus,  on  the  one  hand,  movements  of  the  crust  are  raising  the 
land;  on  the  other,  the  agencies  of  erosion  are  cutting  into 
it  and  removing  its  fragments  toward  the  sea.  There  is  an 
opposition,  or  conflict,  of  two  sets  of  forces,  one  set  tending 
to  raise,  the  other  to  lower  the  surface  of  the  land.  So  far 
the  forces  of  elevation  have  been  more  powerful ;  but  the 
agencies  of  erosion  have  deeply  sculptured  the  lands  and  have 
helped  to  level  the  sea  floor. 

This  conflict  has  been  in  progress  for  many  ages,  and  the 
present  land  surface,  about  which  we  are  to  study,  is  the 
result  of  it.  The  valleys,  which  our  railways  and  canals 
follow ;  the  mountains,  which  act  as  barriers  to  winds  and 
to  the  spread  of    plants,    animals,    and   men;    the   smooth 


22  NEW  PHYSICAL   GEOGRAPHY: 

coastal  plains  ;  the  interior  plateaus  ;  the  harbors  in  which  our 
shipping  gathers ;  the  sites  of  our  leading  cities ;  and  many 
other  land  features  are  a  result  of  the  conflict  between  the 
forces  of  elevation  and  the  agencies  of  erosion. 

Summary.  —  Agencies  of  erosion  —  weather,  rivers,  glaciers,  ivaveSj 
etc.  —  are  cutting  irito  the  land  and  strewing  the  icaste  over  the  sea 
floor.  On  the  other  hand,  forces  of  elevation  are  raising  the  land. 
This  causes  a  conflict,  in  which  the  forces  of  elevation  have  so  far 
been  more  j^otent.  The  present  land  surface,  which  so  greatly 
influences  man,  is  the  result  of  this  conflict. 

15.  The  Continents  —  (A)  Oharacteristics. — A  continent  is 
a  large  upraised  portion  of  the  earth's  crust  nearly  or  quite 
surrounded  by  ocean.  Usually  the  continent  margin  is  sub- 
merged beneath  the  sea  (Fig.  316),  sometimes,  as  off  eastern 
North  America,  for  a  distance  of  50  to  100  miles  from  the 
coast.  At  its  outer  edge  it  is  faced  by  a  steep  slope,  called 
the  continental  slope  (Fig.  116),  which  descends  quickly  to 
the  deep  sea  bottom,  Althougii  the  average  elevation  of  the 
continents  is  but  2000  to  3000  feet  above  sea  level,  when 
measured  from  the  base  of  the  continental  slope  their  average 
height  is  10,000  to  15,000  feet.  Some  portions,  for  example 
the  Dead  Sea,  are  below  sea  level. 

Continents  consist  of  mountain  ranges  with  connecting 
plains  and  plateaus  (Figs,  20,  21).  They  are  crossed  by  riv- 
ers, occupying  valleys,  which  drain  the  land  ;  but  nearly  one 
fourth  of  the  land  has  no  drainage  to  the  sea.  In  these  cases 
the  water  runs  into  interior  basins  or  basins  without  outlet. 

The  outline  of  a  continent  seems  to  be  determined  by  its 
mountain  ranges ;  indeed,  mountains  have  been  called  the  skele- 
tons of  continents.  From  this  standpoint  the  plains  and  plateaus 
may  be  called  its  tissues.  In  fact,  the  plains  and  plateaus  have 
been  built  of  rock  fragments  worn  from  the  mountain  skeleton. 

To  illustrate,  off  eastern  Asia,  from  the  Kurile  Islands  to  the 
Philippines  (Fig.  26),  there  is  a  mountain  cliain  now  rising.  A 
large  part",  of  the  rock  waste  worn  from  these  mouufcains,  and  from 


Fig.  2U.  —  The  main  mouutaiii  axes  of  North  America. 


Fig.  21.  —  Diagram  to  show  the  general  distribution  of  mountains,  plains,  and 

vlateaus  of  the  world. 


Fig.  22. — Relief  map  of  North  America. 


GENERAL  FEATURES  OF  THE  EARTH.  23 

the  mainland,  is  being  deposited  in  the  sea  that  separates  the 
islands  from  the  mainland.  These  deposits  may  in  time  fill  the 
inclosed  sea,  and  a  slight  uplift  of  the  land  may  raise  the  smooth 
sea  bottom  plain,  forming  dry  land,  and  thus  joining  the  mountain 
islands  to  the  coast  of  the  mainland.  It  is  by  similar  changes 
that  continents  have  been  made. 

Summary.  —  Continents  are  uplifted  blocks  of  eartWs  crust  ivhose 
real  margin  is  beneath  sea  level.  They  consist  of  plains,  plateaus, 
and  mountains,  partly  drained  into  interior  basins.  They  oive  their 
outline  to  mountain  skeletons,  connected  by  plains  and  plateaus^  that 
have  been  built  of  rock  fragments  luorn  from  the  mountains. 

(B)  North  America.  —  In  North  America  (Fig.  22)  there 
are  two  great  systems  of  mountains  :  (1)  the  Appalachian 
system,  which  extends  south  westward  from  Labrador  to  Ala- 
bama ;  and  (2)  the  great  western  system,  or  the  western  Cor- 
dilleras^  Avhich  extends  southeastward  from  Alaska  to  Central 
America  (Fig.  20).  A  third  system  of  low  and  very  ancient 
mountains  occupies  the  region  from  Labrador  westward. 
The  vast  plateaus  and  plains  that  connect  these  mountains 
are  largely  made  of  rock  fragments  swept  from  the  moun- 
tains in  past  ages.  Fossil  remains  of  marine  animals  prove 
that  the  rock  strata  were  deposited  in  a  sea,  and  were  later 
raised  by  the  forces  of  elevation  to  form  dry  land. 

Its  triangular  mountain  skeleton  has  given  to  North  Amer- 
ica its  form.  The  continent  is  broad  in  the  north  and  taper- 
ing in  the  south,  because  the  mountains  are  spread  farther 
apart  in  the  north.  Mountains  have  also  caused  some  of 
the  larger  irregularities  of  the  continent.  For  example,  the 
Alaska  and  Labrador  peninsulas  are  the  northern  extension  of 
the  western  and  eastern  mountains  (Fig.  22).  Lower  Cali- 
fornia is  a  southern  extension  of  the  Coast  Ranges  ;  and  the 
Gulf  of  California  is  a  depression  not  yet  filled  with  the  waste 
that  is  being  washed  from  the  bounding  mountains.  The 
peninsulas  and  islands  which  partly  inclose  the  Gulf  of  Mex- 
ico and  Caribbean  Sea  are  also  portions  of  mountain  systems. 


24  NEW  PHYSICAL   GEOGRAPHY. 

Sinking  of  the  land,  which  allows  the  sea  to  enter  the 
valleys,  is  another  cause  for  irregularities  in  the  outline  of  a 
continent.  Such  a  sinking  in  northeastern  America  has  sub- 
merged land  valleys,  forming  Hudson  Bay,  the  Bay  of  St. 
Lawrence,  the  Bay  of  Fundy,  Long  Island  Sound,  New  York 
Harbor,  Delaware  Bay,  Chesapeake  Bay,  and  many  thousands 
of  smaller  bays,  estuaries,  and  harbors.  Where  the  sea  has 
risen  so  as  to  completely  surround  areas  of  higher  land, 
islands  have  been  formed,  such  as  Long  Island,  Newfound- 
land, and  the  thousands  of  others  along  the  northeastern 
;j»nd  northwestern  coasts  of  America. 

Summary.  —  North  America  owes  its  triangular  shape  to  its  moun- 
tain areas,  spread  apart  in  the  north.  The  connecting  plains  and 
plateaus  are  made  of  rock  waste  derived  from  these  mountain  skele- 
tons. The  principal  irregularities  — peninsulas,  hays,  and  islands 
' — are  due  to  two  causes:  (1)  mountains;  (2)  sinking  of  the  land. 

(C)  South  America.  —  South  America  resembles  North 
America  in  its  triangular  form  (Fig.  23).  This  outline  is  due 
to  the  great  mountain  backbone  of  the  Andes  in  the  west,  and 
the  less  prominent  mountain  systems  in  the  north  and  in  east- 
ern Brazil.  South  America  is,  however,  far  more  regular  than 
North  America.  The  only  irregularities  caused  by  moun- 
tains are  in  the  north,  where  the  Andes  system  forms  the 
Isthmus  of  Panama  and  the  small  peninsulas  of  Venezuela. 
The  irregular  southern  coast  is  due  to  sinking  of  the  land;  but 
the  coast  of  Peru  and  northern  Chile  is  now  rising  (p.  36). 

Summary. —  The  mountains  of  South  America  have  given  it  a  tri- 
angular form  a7id  one  or  two  peninsulas  in  the  north;  elsewhere  the 
coast  is  very  regular,  excepting  in  the  south,  where  there  has  been 
sinking. 

(D)  Africa.  —  Like  South  America,  Africa  has  a  triangular  form 
and  regular  outline  (Fig.  24).  Its  outline  is  determined  by  mountain 
uplifts  near  the  coast,  which  have  so  raised  the  interior  that  it  is 
mainly  a  broad  plateau.     Only  one  eighth  of  the  continent  lies 


Fig.  23.  —  Relief  map  of  South  America. 


Fig.  24.  —  Relief  map  of  Af rJica. 


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'"Viti^iifiii  I  '■'■'■'-■ 


GENERAL   FEATURES   OF  THE  EARTH.  25 

below  an  elevation  of  600  feet.  MadagS-scar  is  part  of  a  mountain 
chain  ;  the  peninsula  of  Tunis  is  the  eastern  extension  of  the  Atlas 
Mountains;  and  the  peninsula  of  Abyssinia  is  also  due  to  moun- 
tain uplift.  There  are  few  harbors,  because  there  has  been  no 
extensive  sinking  of  the  land. 

Summary.  —  Africa  is  a  broad  plateau,  triangular  in  outline,  ivitli 
mountains  near  the  coast.     Its  coast  line  is  remarkably  regular. 

(E)  Australia.  —  The  continent  of  Australia  (Fig.  25)  is  a  huge 
island.  A  mountain  chain  in  the  east,  and  others  in  the  west,  have 
helped  determine  its  form ;  but  the  mountains  are  not  so  arranged 
as  to  develop  a  typical  triangular  shape.  York  peninsula  in  the 
northeast,  and  the  peninsula  of  Victoria  and  the  island  of  Tas- 
mania in  the  southeast,  are  continuations  of  the  eastern  Australia 
mountains.  A  sinking  of  this  continent  has  caused  many  small 
bays  and  excellent  harbors. 

Summary.  —  The  island  continent  of  Australia  has  not  the  typical 
triangular  form.  Mountahis  aiid  sinMng  of  the  land  have  caused  a 
S07newhat  irregidar  coast. 

(F)  Eurasia.  —  While  the  other  continents  stand  out  quite 
by  themselves,  Europe  (Fig.  27)  and  Asia  are  so  closely  con- 
nected that  they  are  often  considered  as  one  continent.  Had 
the  study  of  geography  not  started  in  Europe,  it  is  probable 
that  it  would  have  been  called  a  part  of  the  immense  continent 
of  Eurasia  (Fig.  26).  This  great  land  area  has  an  irregular 
triangular  form,  one  angle  of  the  triangle  being  at  Bering 
Strait,  the  second  in  Indo-China,  and  the  third,  in  Spain. 

Eurasia  is  so  mountainous  a  land,  with  mountains  extend- 
ing in  so  many  directions,  that  its  coast  line  is  exceedingly 
irregular.  Its  great  peninsulas  - —  Kamchatka,  Korea,  Indo- 
China,  India,  Arabia,  Greece,  Italy,  Spain,  and  Scandinavia  — 
are  all  due  to  the  presence  of  mountains.  The  numerou 
large  islands,  including  the  Philippines,  the  East  Indies 
Japan,  Sicily,  Corsica,  Sardinia,  and  the  British  Isles,  arv 
also  parts  of  mountains.  Between  these  mountain  uplifts 
are  inclosed  many  bays,  seas,  and  gulfs. 


26  NEW  PHYSICAL   GEOGRAPHY. 

Parts  of  this  land,  especially  northwestern  Europe,  have 
been  lowered  beneath  the  sea.  This  sinking  has  formed  the 
fiords  of  Norway,  the  Baltic,  North,  and  Irish  seas,  and  a 
multitude  of  estuaries,  small  bays,  and  harbors.  It  has  also 
separated  the  British  Isles  from  the  mainland. 

Summary.  —  Europe  is  a  part  of  the  great  Eurasian  continent, 
which  has  a  rough  triangular  form.  The  many  p)eninsulas,  bays, 
islands,  etc.,  are  due  to  mountain  u2)Ufts  and  to  sinking  of  the  land. 

(G)  Influence  of  Continent  Eorms  on  Man.  — The  separation  of 
the  continents  has  interfered  with  the  spread  of  man.  Their  low 
elevation  has  been  very  favorable  to  mankind.  Had  the  average 
elevation  (2000  to  3000  feet)  been  as  great  as  the  average  depres- 
sion of  the  oceans  (12,000  to  15,000  feet),  the  greater  part  of  each 
continent  would  be  too  high  and  cold  to  support  a  dense  popu- 
lation. The  development  of  men  and  nations  has  been  influenced 
in  many  ways  by  the  continent  form,  the  outline  of  its  coast,  the 
inclosed  bays  and  seas,  the  islands,  and  the  distribution  of  moun- 
tains and  plains. 

An  irregular  coast  line  favors  navigation ;  and  it  is  an  interest- 
ing fact  that  the  inhabitants  of  continents  that  have  regular  out- 
lines have  advanced  far  less  rapidly  than  those  whose  coast  has 
many  harbors  and  bays.  Illustrations  of  these  influences  and 
others,  on  man,  animals,  and  plants,  will  appear  in  later  chapters. 

Summary.  —  Tlie  elevation,  surface  features,  and  coast  line  of  con- 
tineyits  have  had  important  influence  on  man,  animals,  and  plants. 

16.  Form  of  the  Oceans.  —  The  continents  are  clustered 
around  the  north  polar  region,  with  tongues  projecting  south- 
ward :  the  ocean  water  is  centered  around  the  south  polar 
region,  with  triangular  tongues  projecting  northward  between 
the  continents  (Fig.  29).  In  outline  the  oceans  are  very  irregu- 
lar, because  the  irregular  continents  form  their  boundaries. 

We  commonly  recognize  five  oceans  (Fig.  28).  It  is 
customary  to  choose  an  arbitrary  boundary  —  the  Antarctic 
circle  —  for  the  ice-laden  Antarctic  Ocean;  but  it  is  far  bet- 
ter to  consider  as  a  great  Southern   Ocean  (Fig.  29)  all  the 


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GENERAL   FEATURES   OF  THE  EARTH. 


27 


water  south  of  Australia,  Africa,  and  South  America.     Three 
great  ocean  tongues  extend  northward  from  this  Southern 


180 


180 


to  Do 

Fig.  29.  —  The  northern  and  southern  hemispheres. 

Ocean:  (1)  the  Indian  Ocean^  which  reaches  up  to  Asia 
between  Australia  and  Africa ;  (2)  the  immense  Pacifie^ 
which  extends  up  between  America,  Australia,  and  Asia,  to 
the  point  where  America  and  Asia  almost  meet ;  and  (3)  the 
Atlantic  tongue,  bounded  by  the  Americas  on  one  side  and 
Africa  and  Europe  on  the  other.  The  Atlantic  is  given  an 
hour-glass  shape  by  the  narrowing  wiiere  the  projection  of 
South  America  reaches  eastward  toward  that  of  Africa. 
The  Arctic  Ocean 
is  an  extension  of 
the  Atlantic;  it  is, 
in  fact,  an  ice-cov- 
ered bay,  partly 
cut  off  from  the 
Atlantic  by  Green- 
land and  Iceland.  ^ 

Fig.  30.  —  The  land  and  water  hemispheres. 
T  h  e     n  o  r  t  h  e  rn 
hemisphere  contains  the  greater  part  of  the  land,  while  the  south- 
ern hemisphere  is  essentially  a  water  hemisphere  (Fig.  29).     By 
choosing  the  proper  circle,  it  is  possible  to  so  divide  the  earth  a? 


28  NEW  PHYSICAL   GEOGRAPHY, 

to  have  one  hemisphere  in  which  most  of  the  land  is  placed,  and 
the  other  with  little  land  (Fig.  30).  London  is  very  near  the 
center  of  the  land  hemisphere. 

Now  that  men  no  longer  timidly  skirt  the  coasts  in  small' 
boats,  but  steer  boldly  out  to  sea  in  great  ships  that  visit 
every  ocean,  the  needs  of  ocean  navigation  have  led  to  the 
making  of  canals  for  short  cuts  across  land  barriers.  For 
merly,  vessels  sailing  from  Europe  to  India  went  all  the  way 
around  Africa  ;  now  they  take  a  short  cut  across  the  Isthmus 
of  Suez  (Fig.  535).  Soon  ships  from  eastern  United  States 
and  Europe,  bound  for  Asia  or  western  United  States,  will 
make  a  short  cut  by  way  of  the  Isthmian  Canal.  Thus 
every  day  the  oceans  are  becoming  more  useful. 

Summary. — 3Tost  of  the  ocean  water  is  in  the  southern  hemi- 
sphere, three  triangular  tongues  extending  from  the  great  Southern 
ocean  northivard  between  the  continents.  The  Arctic  is  a  bay-like 
extension  of  the  Atlantic. 

Topical   Outline,    Questions,   and   Suggestions. 

Topical  Outline.  —  8.  The  Atmosphere.  —  Extent;  composition; 
proof  of  its  existence ;  importance,  —  life,  fire,  decay,  diffusion  of  light 
and  heat,  hearing,  winds,  vapor,  wind  power;  effects  on  land  ;  soil. 

9.  The  Oceans.  —  Distribution  of  water;  area  covered;  depth;  im- 
portance,—  animal  products,  navigation,  vapor  supply,  effect  on  climate. 

10.  The  Solid  Earth.  —  Covering  of  sea  floor  ;  of  land;  origin  of  soil; 
importance;  depth;  absence  on  steep  slopes ;  condition  beneath  the  soil 
mantle ;  valuable  mineral  substances. 

11.  The  Earth's  Interior. — Weight  of  material  of  outer  part  and  of 
interior  ;  proofs  of  interior  heat ;  former  belief  ;  earth's  crust ;  reasons  for 
present  belief  ;  effects  of  pressure ;  former  condition  of  earth  ;  future. 

12.  Air,  Water,  and  Rock. —  (a)  States  of  matter:  air,  water,  and  rock 
illustrate  the  three  states ;  changes  of  each  of  these  to  the  other  two  states. 
(b)  Intermi;igling :  rock  and  water  in  air ;  water  and  air  in  earth  ;  air 
and  rock  material  in  water. 

13.  Irregularities  of  the  Earth's  Crust.  —  Average  depth  of  ocean 
basins;  average  height  of  continents;  proportion  of  plains  ;  distribution 
of  mountains  and  volcanoes ;  amount  of  irregularity  of  earth's  surface ; 
cause  of  irregularities;  changes  in  leveL 


GENERAL  FEATURES  OF  THE  EARTH,  29 

14.  Conflict  of  Erosion  and  Elevation.  —  Nature  of  agencies  of  erosion , 
effect  on  land;  on  sea  floor;  conflict  between  erosion  and  elevation; 
importance  of  result  upon  man. 

15.  The  Continents.  —  (^4)  Characteristics:  definition;  real  bounda- 
ries ;  elevation ;  surface  features ;  drainage ;  relation  of  mountains  to 
continent  form  —  illustration.  (B)  North  America:  mountain  systems; 
relation  to  continent  form;  to  plains  and  plateaus;  to  irregular  outline; 
effect  of  sinking  of  the  land.  (C)  South  America  :  mountains;  outline; 
irregularities.  (D)  Africa :  outline ;  surface  features ;  coast  line. 
(E)  Australia:  position;  form;  coast  line.  (F)  Eurasia:  relation 
between  Europe  and  Asia;  form  of  Eurasia;  effect  of  mountains  on 
coast  line;  of  sinking  of  the  land.  (G)  Influence  of  Continent  Forms  on 
Man :  effect  of  separation  ;  of  low  elevation  ;  of  coast  line. 

16.  Form  of  the  Oceans. —  General  form  and  outline;  subdivisions  of 
the  ocean  waters;  boundaries  of  each;  land  and  water  hemispheres; 
value  of  oceans  for  navigation. 

Questions.  —  Section  8.  What  is  the  extent  of  the  atmosphere  i 
Name  some  important  effects  of  the  air. 

9.  What  influence  has  gravity  on  the  oceans  ?  What  is  the  area  and 
depth  of  the  oceans?  Of  what  importance  is  the  ocean  for  its  animal 
products ;  for  navigation  ;  for  its  influence  on  climate  ? 

10.  What  covers  the  sea  floor?  The  land?  What  is  the  origin  of 
soil?  Of  what  value  is  it?  What  is  beneath  it?  Why  is  it  sometimes 
absent?     What  valuable  materials  come  from  the  solid  earth? 

11.  What  reasons  are  there  for  believing  the  earth's  interior  to  be 
highly  heated?  Why  is  it  no  longer  believed  to  be  molten?  What 
prevents  it  from  melting?     What  is  the  earth's  crust? 

12.  How  do  the  states  of  air,  water,  and  rock  vary?  What  are  the 
three  states  of  matter?     How  are  air,  water,  and  rock  mingled? 

13.  Compare  the  ocean  depths  and  continent  elevations.  What  is  the 
general  condition  of  ocean  bottoms  and  continents?  Where  are  moun- 
tains found?  How  many  times  greater  is  the  earth's  diameter  than  the 
height  of  Mt.  Everest?     What  is  the  cause  of  these  irregularities? 

14.  What  agencies  are  attacking  the  land?  What  effect  has  this 
attack  on  the  land?  On  the  sea  floor?  What  conflict  is  there  between 
opposing  forces  ?     How  has  this  conflict  been  of  importance  to  man  ? 

15.  (^)  What  are  the  characteristics  of  a  continent?  What  relation 
do  the  mountains  have  to  the  continent  form?  Give  an  illustration. 
{B)  Explain  the  general  form  of  North  America.  Explain  the  irregu- 
larities of  the  outline.  Give  instances  illustrating  each  of  the  two  causes 
for  irregularities.  (C)  What  are  the  characteristics  of  South  America? 
(2))    Of  Africa?     {E)   Of   Australia?     (F)    What   is  the   relation   of 


30  NEW  PHYSICAL   GEOGRAPHY. 

Europe  to  Asia  ?  Explain  the  irregular  outline  of  Eurasia.  (G)  How 
has  the  continent  form  influenced  man? 

16.  State  the  distribution  of  the  ocean  water :  its  general  distribu- 
tion ;  the  subdivisions,  starting  from  the  Southern  Ocean ;  the  meaning 
of  land  and  water  hemispheres.     What  obstacles  have  been  overcome? 

Suggestions. —  (1)  In  a  small  jar  seal  up  a  plant,  being  careful  to 
have  it  well  watered,  and  see  if  it  grows  after  the  oxygen  is  exhausted. 
(2)  Place  a  candle  in  a  fruit  jar,  light  it  and  see  if  it  burns  after  the 
oxygen  is  used  up.     (3)  Why  are  there  holes  beneath  the  flame  of  a  lamp  ? 

(4)  Have  some  oxygen  generated  in  the  chemical  laboratory,  and  place 
in  it  a  smouldering  piece  of  cloth.     Explain  the  change  that  occurs. 

(5)  How  deep  is  the  soil  in  your  vicinity  ?  Find  some  cut  —  a  cellar, 
railway  cut,  or  stream  valley,  —  where  bed  rock  is  seen  beneath  the  soil. 
How  thick  is  the  soil  ?  Of  what  is  it  composed  ?  What  kind  of  rock 
underlies  it?  Is  the  line  between  rock  and  soil  a  sharp  line?  (6)  To 
illustrate  the  three  states  of  matter :  freeze  some  water.  Melt  the  ice, 
then  evaporate  the  water  over  the  fire.  Where  does  the  water  go  ?  Place 
some  water  in  a  shallow  pan  in  a  room  and  watch  it  from  day  to  day. 
Where  does  it  go ?  What  becomes  of  the  water  that  3''0u  pour  on  plants? 
Of  that  sprinkled  on  the  city  pavements  ?  (7)  Sth'  mud  and  water 
together.  Have  you  ever  seen  a  stream  resembling  the  muddy  water  ? 
Where  did  the  mud  come  from  ?  Where  was  it  being  carried  ?  (8)  Care- 
fully weigh  a  piece  of  chalk.  Soak  it  in  water  and  weigh  it  again.  Why 
the  difference  ?  Most  rocks  will  illustrate  the  same  thing,  but,  being  less 
porous,  not  so  well  as  chalk.  (9)  Place  some  salt  in  water  and  stir  it 
once  in  a  while.  Where  has  the  salt  gone?  After  twenty-four  hours 
pour  the  water  off  and  evaporate  it.  Do  you  find  the  salt?  Chalk, 
marble,  and  many  mineral  substances  will  dissolve  as  the  salt  did,  but  in 
smaller  quantities.  (10)  See  if  there  are  fossils  in  the  rocks  of  your 
neighborhood.  If  so,  find  out  if  they  once  lived  in  the  sea.  What  do 
they  prove  ?  (11)  In  a  shallow  pan  of  water  build  three  ridges  of  pebbles 
and  clay,  as  high  as  you  can,  forming  a  triangular  outline  to  represent 
the  mountain  skeleton  of  North  America.  With  a  sprinkling  pot  wear 
them  partly  down.  Draw  off  the  water  with  a  siphon,  then  make  a  sketch 
map  of  the  miniature  continent,  marking  on  it  the  position  of  the  moun- 
tain ridges.     Compare  it  with  an  outline  m&p  of  North  America. 

Reference  Books.  —  See  references  at  end  of  Chapters  III,  X,  and  XII  ; 
also  Mill,  International  Geography,  Appleton  &  Co.,  New  York,  $  3.50. 


CHAPTER   III. 

CHANGES   IN   THE   EARTH'S    CRUST. 

17.  Relation  of  Man  to  the  Land.  —  In  a  railway  journey 
from  Atlantic  City,  east  of  Philadelphia,  to  Chicago  a  great 
variety  of  land  forms  may  be  seen.  First  the  seashore  ;  then 
a  lowland  plain  ;  then  a  hilly  country  ;  then  a  wild  mountain 
region,  with  long  ridges  separated  by  broad  valleys ;  then  a 
rugged  plateau,  with  rivers  deeply  set  between  steeply  rising, 
wooded  banks  ;  then  the  open  plains.  Besides  these  large  fea- 
tures many  smaller  ones  are  noticeable — rivers,  creeks,  brooks, 
rapids,  waterfalls,  floodplains,  lakes,  narrow  gorges,  broad  val- 
leys ;  in  fact,  all  the  great  variety  of  land  forms  to  be  found 
in  a  large  area  of  diversified  country. 

The  careful  observer  will  also  note  the  following  facts 
regarding  settlement  and  industry.  The  steeper  hill  and 
mountain  sides  are  still  forested  (Fig.  85),  and  lumbering  is 
the  only  industry  on  their  rocky  slopes.  Few  houses  are  seen 
in  the  narrow,  valleys,  though  here  and  there  a  fall  has  given 
the  site  to  a  mill,  or  even  to  a  town;  and,  in  a  few  places,  there 
is  some  industry  connected  with  the  production  of  valuable 
minerals  from  the  mountain  rocks.  On  the  other  hand, 
the  open  plains  and  low  hills,  both  to  the  east  and  west  of 
the  mountains,  are  everywhere  inhabited  ;  houses  are  almost 
always  in  sight,  woods  are  scattered,  farms  are  seen -on  every 
hand,  and  the  land  is  dotted  with  villages,  towns,  and  cities. 

This  route  passes  three  of  the  largest  eleven  cities  in  the 
United  States,  —  Chicago  the  second  in  size,  Philadelphia  the 
third,  and  Pittsburg  the  eleventh.  One  is  a  sea  port,  one  a 
lake  port,  and  one  a  river  port. 

31 


32  NEW  PHYSICAL   GEOGRAPHY, 

These  few  facts  indicate  that  there  is  a  relation  between 
the  form  of  the  land  and  the  industries  of  the  people.  Every 
educated  person  should  know  the  causes  which  operate  to  so 
modify  the  form  of  the  land  as  to  adapt  it  to  different  indus- 
tries. This  inquiry  belongs  to  physical  geography,  or,  as  itis 
often  called,  physiography.  To  truly  appreciate  this  subject 
it  is  necessary  to  carry  our  inquiry  back  far  enough  to  under- 
stand some  geological  facts  and  principles ;  and  to  this  the 
present  chapter  is  largely  devoted. 

Summary.  —  There  are  great  differences  in  the  land  surface  from 
place  to  place,  and  consequently  in  the  industries  of  man.  Physical 
Geography,  or  Physiography,  studies  the  causes  for  these  differences 
and  their  relation  to  one  another. 

18.  Rocks  of  the  Crust. ^  —  The  many  different  kinds  of 
rocks  in  the  earth's  crust  are  included  in  three  large  classes, 
—  sedimentary,  igneous,  and  metamorphic. 

(A)  Sedimentary  Hocks. — Rock  fragments — pebbles,  sand, 
and  clay  —  are  washed  into  seas  and  lakes  by  rain,  rivers,  and 
waves.  They  settle  in  the  quiet  water,  the  coarser  fragments 
sinking  to  the  bottom  first.  The  motion  of  the  water,  agi- 
tated by  waves  and  currents,  keeps  the  finer  fragments 
suspended  for  a  longer  time,  and  they  therefore  sink  to  the 
bottom  farther  from  shore.  Thus  the  water  assorts  the  rock 
fragments  according  to  size. 

On  some  days  the  waves  and  currents  are  weak,  on  others 
strong ;  sometimes  the  rivers  bring  little  sediment,  at  other 
times  much.  These  differences  in  currents,  and  in  materials 
supplied,  cause  the  deposit  of  layers  of  different  kinds,  one 
on  another.  Each  layer  is  of  the  kind  that  waves  and  cur- 
rents are  able  to  bring  (Fig.  35). 

Such  layers  are  called  strata  (singular,  stratum'),  and  the 
rock  is  said  to  be  stratified.  Some  strata  are  thin,  others 
thick.     Sometimes  only  one  stratum  is  seen  in  a  cliff,  while  in 

1  Appendix  C  contains  a  description  of  common  minerals  and  rocks. 


—  A  shale  clili  iu  a  gorge.    Some  of  the  layers  are  slightly  moic  sand 
than  the  clay  shales  which  form  most  of  the  cliffs. 


Fia.  32.  —  A  gravel  bank,  with  some  layers  partly  consolidated,  and  tnerefore 

standing  out  from  the  face  of  the  bank. 


Fig.  33.  —  Granite,  lower  left  hand  figure;  pumice,  upper  left  hand; 

gneiss,  right  hand. 


Fig.  34.  — To  illustrate  the  origin  of  igneous  rocks.    The  cone  on  the  left  is  a 
volcano,  made  of  lava  and  volcanic  ash. 


CHANGES  IN  THE  EARTH'S   CRUST. 


33 


other  cliffs  there  are  strata  of  different  kinds  (Fig.  31),  pos- 
sibly shale,  sandstone,  conglomerate,  and  limestone. 

^Vhen  the  sediment  is  deposited,  it  is  loose  and  unconsolidated, 
like  a  gravel  bank.  The  pressure  of  other  layers,  deposited  above, 
and  the  action  of  percolating  water,  slowly  bind  the  fragments  to- 
gether, forming  solid  rock.  The  percolating  water  dissolves  min- 
eral substances  in  one  place,  carries  them  on,  and  deposits  some 
around  the  sediment  grains.     This  binds,  or  cements,  the   rock 


Fig.  35.  —  To  illustrate  the  deposit  of  sedimentary  rocks.  On  the  extreme  left 
are  coarse  pehbles;  on  the  extreme  right,  clay;  in  the  middle,  sand.  Some 
layers  of  pebbles  were  dragged  out  to  the  sand  area  when  the  currents  and 
waves  were  strong;  and  some  sand  layers  were  stratified  with  the  clay  strata. 

fragments  together.  The  most  common  rock  cements  are  the 
common  soluble  minerals,  carbonate  of  lime,  oxide  of  iron,  and 
quartz.  One  may  often  see  the  process  of  cementing  in  a  gravel 
bank  (Fig.  32)  where  a  white  coating  of  carbonate  of  lime  has 
been  deposited  on  some  of  the  pebbles. 

Summary.  —  Sedimentary  rocks  are  in  layers,  or  strata,  formed 
by  the  assorting  power  of  iva.ves  and  cnrrents,  which  vary  in  strength 
and  carry  finer  particles  farther  from  shore  thaii  the  coarser  particles. 
By  pressure  and  the  deposit  of  mineral  ce'nients,  the  loose  rock  frag- 
ments are  hound  together,  forming  solid  rock. 

(B)  Igneous  Roeks.^  —  These  rocks  have  risen  from  within 
the  earth  in  a  melted  state.  In  some  cases  each  eruption  pro- 
duces a  lava  flow,  which  cools  to  form  a  thick,  massive  layer 
of  solid  rock.     In  other  cases  the  violence  of  the  eruption 

1  See  also  Chapter  VII. 


34  NEW  PHYSICAL   GEOGRAPHY, 

blows  the  lava  into  bits  of  volcanic  ash  or  porous  pumice 
(Fig.  33).  Lava  and  ash  usually  build  a  cone  around  the 
volcanic  vent  or  neck  (Fig.  34).  Such  beds  are  usually  less 
regular  and  more  massive  than  sedimentary  strata. 

Much  lava  fails  to  reach  the  surface.  Such  intruded  igneous 
rock  is  found  in  various  positions,  cutting  across  the  sedimentary 
and  other  rocks.  A  narrow  crack  filled  with  lava  forms  a  dike 
(Fig.  34) ;  a  mass  of  lava  thrust  between  strata  forms  an  intruded 
sheet  or  sill  (Fig.  34) ;  large,  irregular  masses,  rising  into  the  cores 
of  mountains,  form  bosses  (Fig.  34).  Pikes  Peak  and  many  other 
peaks  are  bosses  of  hard  granite  rock  (Fig.  33),  brought  to  light 
by  the  wearing  away  of  the  layers  into  which  they  were  intruded. 

Summary.  —  Igneous  rocks  are  formed  by  the  cooling  of  melted 
lava,  some  at  the  surface,  in  the  form  of  lava  flows  and  volcanic  ash, 
some  as  intruded  dikes,  sheets,  and  bosses. 

(C)  Metamorphic  Hocks.  —  When  subjected  to  great  pressure,  or 
heat,  or  both,  rocks  are  changed,  or  metamorphosed.  By  metamor- 
phism  limestone  is  altered  to  marble ;  shale  to  slate  ;  and  sand- 
stone to  quartzite.  The  change  may  go  so  far  that,  as  in  the  case 
of  gneiss  (Fig.  33)  and  schist,  it  is  often  impossible  to  tell  the 
nature  of  the  original  rock.  Metamorphic  rocks  are  especially 
common  among  mountains  where,  during  the  mountain  formation, 
the  strata  have  been  subjected  to  great  pressure  and  heat.  These 
changes  have  bent,  folded,  broken,  and  twisted  the  layers  (Fig. 
46),  and  often  completely  altered  the  rocks  from  their  original 
condition. 

Summary.  —  When  subjected  to  heat,  pressure,  or  both,  as  among 
mountains,  rocks  are  greatly  altered  or  metamorphosed. 

(D)  Resistance  of  Rochs.  — All  minerals,  when  exposed  to 
the  weather,  are  attacked  by  the  elements  ;  but  there  is  much 
difference  in  the  rate  at  which  different  ones  wear  away. 
Quartz,  for  example  (Appendix  C),  is  liard,  only  slightly- 
soluble,  and  does  not  decay  ;  feldspar  is  hard  and  does  not 
dissolve,  but  decays  without  great  difficulty  ;  calcite  is  both 
soft  and  easily  soluble. 


CHANGES  IN   THE  EARTH'S   CBUST.  35 

The  rate  of  decay  of  rocks  depends  in  large  part  on  the 
kind  of  minerals  of  which  they  are  composed.  Sandstone 
and  quartzite  (Appendix  C),  made  mainly  of  quartz,  are 
usually  very  durable  rocks  ;  and  so  is  granite,  which  is  mostly 
quartz  and  feldspar.  On  the  other  hand,  limestone  and 
marble,  made  of  calcite,  are  easily  destroyed. 

The  decay  of  minerals  and  rocks  is  due  largely  to  the 
action  of  water  (p.  38).  Hence  dense  and  massive  rocks, 
like  gneiss  and  granite,  are  not  so  easily  disintegrated  as 
porous  or  friable  ones,  like  shale  and  schist,  into  which 
water  enters  easily.  Because  of  these  facts  weak  rocks  are 
■»^/orn  away,  forming  valleys,  while  durable  rocks  are  left 
standing  to  form  hills,  ridges,  and  peaks  (Fig.  38). 

Summary.  —  Some  minerals  and  rocks  are  durable,  others  iveak. 
TJierefore,  as  the  land  wears  down,  valleys  are  formed  where  the 
rocks  areiveak;  hills,  ridges,  and  peaks  where  they  are  more  durable. 

19.  Changes  in  Level  of  the  Land.  — The  old  ideas,  that  the 
hills  are  everlasting  and  that  the  land  is  firm  and  stable,  are 
now  known  to  be  incorrect.  On  the  contrary,  the  land  is 
ever  changing.  Hills  are  slowly  wearing  away,  valleys  are 
being  deepened,  and  the  waste  is  being  carried  to  the  sea. 

In  addition  to  this,  the  crust  of  the  earth  is  slowly  rising 
in  some  places  and  sinking  in  others.  By  these  movements 
sea  bottoms  have  been  raised  to  form  parts  of  continents ; 
mountains  have  been  formed ;  and  lands  have  been  lowered 
beneath  the  sea.  The  explanation  of  these  changes  is  the 
slow  cooling  and  contraction  of  the  heated  interior  (pp.  17 
and  99). 

Evidence  of  such  changes  in  level  during  past  ages  is  abun- 
dantly preserved  in  the  rocks.  Beaches  and  coral  reefs  are 
found  many  feet  above  the  sea;  and  fossil  remains  of  ocean 
animals  are  entombed  in  the  strata,  even  of  mountains.  There 
is  also  full  proof  that  changes  of  level  are  now  in  progress. 
For  example  :  a  part  of  the  Scandinavian  peninsula,  north  of 


36 


NEW  PHYSICAL   GEOGRAPHY. 


Stockholm,  has  risen  7  feet  in  150  years ;  the  Netherlands 
are  slowing  sinking ;  the  coast  of  New  Jersey  is  sinking  at 
the  rate  of  about  2  feet  a  century ;  Eskimo  houses  in  Green- 
land have  been  lowered  into  the  sea ;  the  land  around  the 
Great  Lakes  is  slowly  rising ;  and  in  1822,  and  again  in 
1835,  the  coast  of  Chile  was  raised  2  to  4  feet.  Hundreds  of 
dmilar  cases  are  known  (Fig.  37). 

These  changes  of  level  are  of  two  kinds :  (1)  rapid  and  local, 
where  moiiutains  are  now  growing,  as  in  Japan  and  western 
South  America ;  and  (2)  slow  and  widespread,  where  large  areas 
slowly  swing  up  or  down,  as  in  northeastern  America  (p.  208). 
While  in  some  places  the  lands  are  sinking,  as  a  general  rule  they 
are  rising.  This  has  been  true  for  long  periods  of  the  past ;  and, 
as  a  result,  the  continents  are  very  largely  made  of  sedimentary 
strata  that  were  deposited  in  ancient  seas. 

Summary.  —  The  surface  of  the  land  is  slowly  loearing  aiuay;  it  is 
also  being  raised  here  and  lowered  there.  There  are  both  local 
rapid  movements  and  a  slow  sivinging  uj)  or  clown  of  large  areas. 
On  the  whole,  the  continents  have  beeri  rising,  and  this  is  why  they 
are  so  largely  made  of  sedimentary  strata. 

20.  Disturbance  of  the  Strata.  —  The  sedimentary  strata 
are    deposited   in   nearly  horizontal   layers   parallel   to   the 

sea  floor  (Figs.  35,  43).  When 
added  to  the  land  these  strata  are 
usually  raised  by  slow,  broadly 
extended  movements  which  only 
slightly  disturb  the  original 
horizontal  position  (Fig.  31). 
The  plains  of  the  Atlantic  coast 


I iiliim » 


''"•(farstn'S'at  d^iffeSr it^'eU   -"^  the    Mississippi  valley,  and 

on  the  two  sides  of  the  fault  the   plateaus  of  the  West,  have 

P^^"®-  such  horizontal  strata. 

Among  mountains,  on  the  other  hand,  the  strata  are  folded 

and  broken  by  the  great  pressure.     In  such  cases  the  layers 

are  no  longer  horizontal,  but  are  tilted  at  all  angles  (Fig.  38). 


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CBANGES  IN  TBE  EARTH'S  CRUST. 


37 


Fig.  39.  —  An  anticline. 


Lava  and  meta- 
morphic  rocks  (p. 
34)  are  also  com- 
mon in  mountain 
regions.  For  these 
reasons  mountain 
rocks  are  far  more 
complex  in  kind 
and  position  than 
those  of  plains. 

Various  names 
have  been  given  to 
the  forms  assumed 
by     the      disturbed 

mountain  strata.  A  break  in  the  rocks,  accompanied  by  move- 
ment on  one  side,  is  known  as  2^.  fault  (Figs.  36,  44).  An  arched 
upfold  of  the  strata  is  known  as  an  a>/^/c/me  (Figs  39,  45);  a 
downfold  is  a  syndine  (Fig.  40).  In  an  anticline  the  rocks  in- 
cline, or  dip  (Figs. 
38, 39, 45),  both  ways 
from  the  axis  of  the 
fold ;  in  a  syncline 
they  dip  toward 
the  axis  (Fig.  40). 
Where  a  fold  has  a 
dip  in  only  a  single 
direction  it  is  called 
a  monocUne  (Fig. 
41).  Some  folds 
are  very  regular  or 
symmetrical  (Fig. 
45) ;  others  are 
quite  unsymmetrkal 
(Fig.  42)  ;  and  in 
some,  the  folding  has  gone  so  far  thac  the  folds  are  actually  over- 
turned (Figs.  42,  48).  In  very  intense  folding  the  strata  are  some- 
times crumpled  (Fig.  46). 


Fig.  40.  —  A  syncline. 


§8 


NEW  PHYSiCAL   GEOGRAPHY. 


During  their  uplift,  rocks  are  often  cracked  by  the  strains. 
These  cracks  are  called  Jom^p/anes  (Figs.  47, 75).  The  joint  planes 
usually  extend  vertically  into  the  strata,  and  consist  of  two  sets, 
meeting  nearly  at  right  angles.     Water  readily  enters  along  these 

natural  planes  of 
splitting  (Fig.  51), 
which  therefore  aid. 
in  disintegrating  the 
rocks.  Joint  planes 
are  of  great  impor- 
tance in  quarrying, 
for  they  make  natu- 
ral breaks  which  aid 
in  splitting  out  blocks 
Fig.  41. — A  monocliue.  of  stone. 


eORMAY  &  CO.,  N.V. 


Summary.  —  In  plains  and  jilateaus  the  uiMfted  stratified  rocks 
are  commonly  left  in  nearly  their  original  horizontal  position  ;  hut  in 
mountains  they  are  folded  and  faulted.  Joint  planes ,  or  natural 
planes  of  breakage,  are  also  produced  by  the  strains. 

21.  Agents  of  Weathering.  —  When  exposed  to  the  air, 
rocks  crumble  and  fall  apart  as  wood  and  nails  do.  This  dis- 
integration, or  weathering^  is  due  to  the  action  of  various 
agencies,  the  most  important  of  which  are  percolating  water, 
air,  and  the  action  of  animals  and  plants.     These  agencies  do 


Fig,  42.  —  Section  of  unsymmetrical  and  overturned  folds. 

some  of  their  work  by  dissolving  and  decaying  minerals,  some 
by  mechanical  means,  as  when  rocks  are  ruptured  by  frost. 

Summary.  —  Rocks  crumble,  or  iveather,  by  the  mechanical  and 
chemical  action  of  percolati7ig  water,  air,  and  animals  and  plants. 


^...,..,.,... 

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Fig.  43.  —  Horizontal  strata  in  the  West.  A  hard  Ftg.  44.  —  A  fault.  No- 
layer,  standing  out  as  a  low  cliff,  may  be  seen  in  tice  that  the  layers 
the  foreground  and  far  along  the  hillside.                          do  not  match  on  the 

two  sides  of  the  fault 
plane. 


$--.'^ 


V 


Fig.  45.  —  A  symmetrical  anticline. 


Fig.  46.  —Crumpled  layers  lu  Dauada.     Notice  how  couioiied  they  are. 


FiQ  47.  — Joint  planes  on  the  shores  of  Lake  Cayno:a,  New  York.  The  two 
sets  almost  vertical,  meet  at  nearly  right  angles.  The  smooth  faces  of  the 
cliff' are  due  to  the  fact  that  the  rock  has  cleaved  away  from  it  along  the 
^oint  planes. 


CHANGES  IN  THE  EARTH'S   CRUST, 


39 


22.  "Work  of  Underground  Water.  —  A  portion  of  each  rain 
sinks  into  the  soil,  and  part  of  it  percolates  into  the  rocks, 
for  underground  water  is  able  to  enter  even  the  densest  of 
rocks.  Some  of  this  water  enters  along  joint  planes  (Figs. 
51,  54) ;  some  between  the 
rock  grains;  and  some 
along  the  cleavage  planes 
of  the  minerals. 

In  moist  climates,  shal- 
low wells  find  this  under- 
ground water  even  in  rock; 
and  upon  it  farms  and  en- 
tire towns  and  villages  de- 
pend for  drinking  water. 
It  is  underground  water, 
too,  that  the  roots  of  plants 
seek  in  the  soil.  Without 
it  they  die.  Its  presence  is 
furtlier  shown  by  springs, 
which  are  places  where 
underground  water  rises 
to  the  surface  in  some 
quantity  (p.  59). 

Underground   water 
find's  many  mineral  substances  which  it  is  able  to  take  away 
in  solution.     Its  power  of  solution  is  greatly  increased  by 
carbon  dioxide,  and  other  substances,  which  it  obtains  from 
the  air  and  from  deca3dng  vegetation. 

Aided  by  oxygen,  carbon  dioxide,  and  other  substances,  the 
underground  water  also  causes  changes  in  composition  of 
many  minerals.  These  changes  are  not  very  unlike  that 
which  causes  a  shiny  nail,  when  exposed  to  dampness,  to 
decay  to  a  yellow,  powdery  iron  rust.  By  these  changes 
some  substances  are  produced  which  the  percolating  water 
qan  carry  off  in  solution.     The  roots  of  plants  seek  and  obtain 


Fig.  48.  —  A  small,  overturned  fold  —  both 
a  syncliue  and  an  anticline. 


40 


NEW  PHYSICAL  GEOGRAPHY. 


Fig.  4U.  —  A  mountain  top,  showing  the  rock  shattered 
by  frost  action. 


some  of  these  soluble  mineral  products,  which  are  plant  food. 

This  decay,  together  with  removal  of  portions,  causes  mineral? 

and  rocks  to  crumble. 

In  cold  climates  the  mechanical  work  of  water  is  of  impor- 
tance in  disinte- 
grating rocks. 
The  water,  in  the 
soil,  in  the  joint 
planes,  and  in  the 
microscopic  rock 
crevices,  freezes 
in  winter.  When 
water  freezes  it 
m ust  expand ;  and , 
as  a  bottle  breaks 
when  water  f«reezes 
in  it,  so  in  winter 
the  rocks  are  often 

broken  by   frost  action.     This  frost  work  is  an  important 

agent  of  rock  disintegration  (Figs.  49,  52,  54). 

Summary.  —  Water  percolates  into  soil  and  even  rock.  It  dis- 
solves some  minercds,  changes  others,  and  thus  causes  the  rocks  to 
disintegrate.     In  cold  climates,  frost  also  aids  in  disintegration. 

23.  Influence  of  Air  in  Weathering.  —  Warming  causes  rocks  to 
expand,  and  cooling  causes  them  to  contract.  A  fire  built  against 
a  rock,  for  example,  causes  it  to  expand  and  crack.  In  hot  des- 
erts the  warming  of  rocks  by  day,  and  cooling  by  night,  are  im- 
portant means  of  disintegrating  them. 

The  oxygen  and  carbon  dioxide  of  the  air,  taken  underground 
by  water,  help  in  the  work  of  disintegration;  they  also  cause 
changes  in  damp  soil  and  rock  at  the  surface. 

Summary.  —  Air  helps  in  rock  disintegration  by  its  changes  in 
temperature  and  by  supplying  oxygen  and  carbon  dioxide. 

24.  Organisms  as  Agents  of  Weathering.  —  The  roots  of  plants 
Jielp  to  pry  rock  materials  apart.    In  their  search  for  water  and 


CHANGES  IN  THE  EARTH'S   CRUST.  41 

plaiifc  food,  the  roots  and  tiny  rootlets  enter  any  crevice  to  be 
found  (Fig.  53).  On  growing  larger  they  exert  such  a  pres- 
sure on  the  walls  of  the  crevices  as  often  to  rupture  them. 
In  this  way  soil  is  pulverized  and  rocks  broken  apart. 

The  ash  left  when  wood  is  burned  is  largely  mineral  matter 
that  the  roots  have  taken  as  plant  food.  This  proves  that  plants 
remove  mineral  substances  from  the  soil  and  rock,  and  there- 
fore that  they  help  in  disintegration.  They  aid  also  by  sup- 
plying carbon  dioxide  and  organic  acids  to  water  which,  on 
soaking  into  the  soil,  passes  through  decaying  vegetation. 

Animals  are  likewise  effective  agents  of  weathering.  This  is 
especially  true  of  burrowing  animals,  such  as  earthworms,  moles, 
ants,  woodchucks,  and  prairie  dogs.  They  stir  up  the  soil*  thus 
making  it  more  open  to  the  entrance  of  water ;  tue^  oiia^  son  to 
the  surface,  thus  exposing  it  to  the  weather  ;  and  some,  like  the 
earthworms,  take  soil  into  their  stomachs,  grinding  it  a  little  as 
.it  passes  through.  Earthworms  are  among  the  most  important 
of  agents  in  soil  preparation. 

Summary.  —  Weathering  is  aided  by  plant  roots,  ivJiicJi  pry  off 
fragmeiits  and  remove  miyieral  substances ;  by  carbon  dioxide  and 
organic  acids,  supplied  from  decaying  vegetation  ;  and  by  the  action 
lof  biirrowing  animals,  esjjecicdly  earthworms. 

25.  Rate  of  Weathering. —  Because  the  weather  has  completely 
destroyed  their  form,  it  has  been  necessary  to  replace  certain  stone 
ornaments  (gargoyles)  that  were  placed  on  the  Lincoln  Cathedral, 
\n  England,  about  seven  centuries  ago.  On  the  other  hand,  deli- 
cate scratches  on  rocks,  made  by  glaciers  not  less  than  5000  years 
ago,  are  still  perfectly  preserved  wherever  they  have  been  covered 
by  a  foot  or  two  of  soil  (Fig.  289).  These  facts  show  that  the 
rate  of  weathering  is  slow,  but  that  it  varies  with  circunistances. 

The  nature  of  the  rock  is  one  cause  for  difference  in  the  rate  of 
weathering.     Some  rocks  disintegrate  quickly,  others  slowly. 

Another  cause  for  variation  is  climate.  Where  there  is  little 
moisture,  as  in  deserts,  there  can  be  little  change  due  to  frost, 
solution,  or  decay,  and  weathering  is,  therefore,  very  slow.  An 
obelisk  (Fig.   50),  which  had  stood  for  over  3000  years  in  the 


42 


NEW  PUTSICAL   GEOGRAPHY, 


desert  climate  of  Egypt,  began  to  decay  so  rapidly  when  removed 
to  the  damp  climate  of  New  York  that  it  was  necessary  to  protect 
it  with  a  glaze.  In  cold  climates,  frost  action  is  very  active  ;  in 
hot,  damp  climates  the  abundant  vegetation  supplies  organic  sub- 
stances to  the  warm  percolating  water,  greatly  aiding  it  in  its  worl^ 

of  changing  and  dissolving  the 
minerals. 

Exposure  is  also  of  impor- 
tance in  determining  the  rate 
of  weathering.  Even  a  thin 
soil  cover  protects  the  rock 
from  the  weather.  Rock  frag- 
ments, loosened  by  weathering, 
remain  on  level  surfaces  and 
gentle  slopes,  forming  a  protect- 
ing soil  blanket.  But  on  steep 
slopes,  from  which  the  frag- 
ments fall  away  as  fast  as  they 
are  loosened,  the  rock  is  kept 
constantly  exposed  to  the  ele- 
ments (Figs.  54,  57).  There- 
fore, cliffs,  precipices,  and 
mountain  slopes  are  places  of 
relatively  rapid  weathering. 
That  the  rocks  are  crumbling 
is  proved  by  the  fact  that 
every  now  and  then  a  frag- 
ment falls  from  the  cliffs  (Fig. 
57)  ;  but,  even  in  the  most  favorable  places,  weathering  is  so  slow 
that  one  might  see  no  great  change  in  a  lifetime.  Centuries  are 
required  for  great  changes. 

Summary.  —  Even  uyider  the  most  favorable  conditions,  weathering 
is  very  sloio.  Its  rate  varies  with  the  rock,  climate,  exposure,  and 
steepness  of  slope.  Steep  slopes  are  especially  favorable  because  the 
falling  away  of  loosened  fragments  leaves  the  rocks  exposed. 

26.  Results  of  Weathering.  —  Without  question,  the  most 
important   result   of   weathering    is   the  formation    of   soil. 


Fig.  50.  ~  The  Obelisk  iu  Central  Park. 


a^JdLjLra 


Fig.  51.  —  A  shattered  rocK  surface  showing  many  cracks  into  which  water 

is  able  to  enter. 


Fig.  52.  —  Percolating  water  seep- 
ing out  of  the  rock  and  freez- 
ing. 


Fig.  53.  —  The  routs  ol  a  tree  prying  open 
the  rock  of  a  ledge 


■Hi 


lljiS- 


■..^*^ 


.^. 


1    .      ''.x    ■     ,     i 


'''A  w 


Fig.  54.  —  A  steep  peak  in  the  high  Alps  wliere  frost  action  is  powerful.  Notice 
the  many  cracks  in  the  rock.  Water  enters  along  these,  and  every  now  and 
then  a  fragment  hreaks  away  and  falls  to  the  hase. 


CHANGES  m  THE  EARTH'S  CRUST. 


43 


While  some  of  the  crumbling  rock  is  removed  in  solution, 
there  is  a  remnant,  or  residue^  which  cannot  be  dissolved. 
This  remnant 
forms  residual  soil 
(Figs.  55,  56), 
which  sometimes 
mantles  the  rock 
to  a  depth  of  over 
a  hundred  feet.  A 
large  part  of  the 
land  is  covered  by 
residual  soil,  rest- 
ing on  the  rock 
whose  decay  pro- 
duced it.  Other 
kinds  of  soil  are 
those  brought  by 
wind,  by  rivers, 
and  by  glaciers.     Such  soils  are  not  residual,  but  transported. 

Weathering  supplies  mineral  substances  for  underground  water 


Fig.  55.  —  Residual  soil.    A  few  rouuded  pieces  oi  solid 
rock  remain,  not  yet  completely  disintegrated. 


^ 

:& 


Fig.  56.  —  A  diagram  to  illustrate  the  formation  of  residual  soil.  Notice  that  the 
soil  is  finer  near  the  surface,  where  roots  and  earthworms  penetrate,  and  that 
it  grades  downward  into  solid  rock. 


44  NEW  PHYSICAL   GEOGRAPHY. 

to  remove  in  solution.  It  is  this  that  gives  "  hardness  "  to  water, 
and  the  valuable  properties  to  many  mineral  springs.  One  of  the 
most  common  of  these  dissolved  mineral  substances  is  carbonate 
of  lime,  which  supplies  corals  and  shell-bearing  animals  with  the 
lime  from  which  beds  of  limestone  are  made  in  the  sea. 

Rock  fragments,  loosened  from  cliffs  by  weathering,  gather 
at  the  base,  forming  talus  slopes  (Figs.  67,  66).  Occasionally 
jifreat  masses  are  loosened,  falling  as  landslides  or  avalanches 
(Figs.  58,  161,  162).  There  is  also  a  very  slow,  almost  im- 
perceptible movement  of  rock  fragments  down  even  gentle 
slopes.     It  is  this  that  makes  the  streams  muddy. 

These  rock  fragments  are  used  by  the  rivers  as  tools  (Fig. 
57)  in  cutting  their  valleys;  and,  on  reaching  the  sea,  they 
are  deposited  as  beds  of  sedimentary  rock  (p.  32).  By  this 
removal  of  rock  fragments  and  dissolved  mineral  substances, 
supplied  by  weathering,  valleys  are  being  slowly  broadened. 

Finally,  weathering  is  a  delicate  tool  of  rock  sculpturing. 
It  easily  discovers  which  rocks  are  weak,  and  which  durable; 
and,  by  removing  the  \Veaker  rocks  faster,  it  etches  the  dura- 
ble strata  into  relief  (Figs.  38,  59).  The  importance  of  this 
fact  is  more  fully  shown  in  later  chapters. 

Summary.  —  Among  the  important  results  of  iceathering  not 
already  described  are,  (1)  the  formation  of  residual  soil,  or  soil  of 
rock  decay;  (2)  the  supply  of  soluble  mineral  substances  to  tcater ; 
(3)  the  formation  of  talus  and  avalanches;  (4)  the  supply  of  cutting 
tools  to  rivers;  (5)  the  supply  of  materials  for  the  formation  of  sedi- 
mentary strata;  (6)  valley  broadening ;  and  (7)  rock  sculpturing. 

27.  The  Agents  of  Erosion.  —  Besides  weathering,  which 
disintegrates  the  rock,  thus  preparing  it  for  removal,  there 
are  several  agents  of  erosion  which  remove  and  deposit  rock 
fragments.  The  work  of  these  agents  is  fully  stated  in  other 
chapters  and  now  requires  mere  mention. 

These  agents  are:  (1)  wind,  especially  active  along  the  coast 
(p.  215)  and  in  deserts  (]).  87),  where  there  is  little  vegetation 


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Fig.  58.  —  Au  avalanche  at  Quebec,  just  beueath  the  fortress,  which  destroyed 

a  number  of  houses. 


Fig.  59.  —  A  view  in  the  Colorado  Canyon,  where  the  clitls  have  been  sculptured 
by  weathering  and  erosion,  bringing  the  hard  roclcs  into  relief,  and  giving 
the  softer  strata  more  gentle  slopes. 


CHANGES  IN  THE  EARTH  S  CRUST.  45 

to  protect  the  soil ;  (2)  rivers  (Chapter  IV),  everywhere  at 
work  removing  materials  supplied  by  weathering,  and  at  the 
same  time  often  deepening  their  own  valleys  with  the  rock 
fragments  that  they  carry;  (3)  the  oeean^  whose  waves,  tides, 
and  currents  attack  the  land  along  the  coast  (Chapter  XI), 
and  in  which  sediment  washed  from  the  land  is  deposited 
(pp.  33,  176)  ;  (4)  lahes^  which  resemble  oceans  (p.  220)  ; 
and  (5)  glaciers  (Chapter  VIII),  at  present  important  only 
in  high  mountains  and  in  the  frigid  zones. 

Summary. —  The  agents  of  erosion  —  wind,  rivers,  ocean,  lakes, 
and  glaciers  —  remove  and  deposit  rock  fragments. 

28.  Denudation.  —  The  combined  work  of  the  agents  of  weather- 
ing and  erosion  may  be  called  denudation.  By  denudation  the 
lands  are  being  sculptured  (Fig.  59)  and  their  general  level  lowered. 
If  the  material  removed  by  the  Mississippi  River  were  taken 
equally  from  every  part  of  its  drainage  area,  the  surface  of  the 
valley  would  be  lowered  one  foot  in  6000  years. 

Opposed  to  this  tendency  to  wear  the  land  away  is  the  con- 
stant change  in  level  of  the  land  (p.  35),  by  which  plains  are 
being  raised  above  the  sea,  plateaus  made  higher,  and  mountains 
uplifted  (21).  These  uplifts  are  continually  giving  denudation 
new  work  to  perform.  Were  it  not  for  this  elevation  of  the  land, 
it  is  probable  that  the  continents  would  have  long  since  been 
reduced  nearly  to  sea  level ;  for  the  age  of  the  earth  is  very  great. 

Summary.  —  Denudation  is  the  combined  icork  of  iveathering  and 
erosion.  It  tends  to  lower  the  land;  bat,  though  the  age  of  the  earth 
is  great,  frequent  uplift  has  p>revented  it  from  lowering  the  contineyits 
to  the  condition  of  a  level  plain. 

29.  Age  of  the  Earth. ^  —  No  one  knows  how  old  the  earth 
is.  But  all  who  have  studied  the  question  are  agreed  that  it 
cannot  be  less  than  many  millions  of  years,  and  most  geolo- 
gists hold  that  it  must  be  at  least  a  hundred  million  years. 
The  evidence  of  this  vast  age  cannot  be  stated  in  an  elemen- 

1  For  a  list  of  the  geological  periods,  see  Appendix  D. 


46  NEW  PHYSICAL   GEOGBAPHY. 

tary  book  ;  but  the  following  facts  may  help  the  student  to 
understand  why  it  seems  a  necessary  conclusion. 

So  slow  is  the  work  of  denudation  that  a  person  living  by 
a  river  side,  or  on  the  seashore,  may  see  no  notable  change, 
even  in  a  lifetime ;  yet  careful  study  will  show  that  slow 
changes  are  in  progress.  Geological  study  has  proved  that 
slow  changes  have  accomplished  great  results  in  the  past ; 
and  this  could  not  have  happened  unless  there  had  been  a 
great  length  of  time  involved. 

Among  these  evidences  of  great  changes  are  the  following.  The 
Colorado  E-iver  has  slowly  cut  a  canyon  over  a  mile  in  depth. 
Lofty  mountain  ranges  once  existed  where  New  York  and  Phila- 
delphia now  stand  ;  but  they  have  been  slowly  worn  away.  Volca- 
noes ha  "^v  also  been  worn  down  to  their  very  roots.  To  have  slowly 
accomplished  these  great  results  demands  vast  periods  of  time. 
Sedimentary  rocks  furnish  evidence  leading  to  the  same  conclu- 
sion. It  requires  years  for  a  layer  of  sediment  a  foot  thick  to  be 
deposited;  yet  some  sections  reveal  40,000  feet  of  strata  that  were 
deposited  in  ancient  seas. 

From  these  geological  facts  the  conclusion  that  the  earth 
is  vastly  old  seems  inevitable  ;  and  the  inference  is  supported 
by  evidence  furnished  by  physicists  and  biologists.  Conse- 
quently, all  geologists  and  physical  geographers  are  now  as 
convinced  on  this  point,  as  astronomers  are  that  the  sun  and 
stars  are  millions  of  miles  away.  To  really  appreciate  the 
conclusions  reached  in  the  following  pages,  the  student  must 
start  out  with  the  same  belief. 

Summary.  —  Evidence  furnished  by  geologists,  physicists,  and  biol- 
ogists proves  that  the  age  of  the  earth  is  many  millions  of  years. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  — 17.  Relation  of  Man  to  the  Land.  —  Changes 
noted  on  a  railway  journey:  larger  features ;  smaller  features;  indus- 
tries; cities;  relation  between  land  form  and  industries. 

18.  Rocks  of  the  Crust.  —  Three  divisions.  (A)  SeiJimentary  rocks: 
manner  of  deposit;   terms  used:  consolidation.     (B)  Igneous  rocks:  on 


CHANGES  IN   THE  EARTH'S   CEUST.  47 

the  surface ;  intruded  into  the  crust.  (C)  Metamorphic  rocks :  cause ; 
results;  metamorphisni  in  mountains.  (D)  Resistance  of  rocks:  differ- 
ences in  minerals  ;  in  rocks ;  eifect  on  land  form. 

19.  Changes  in  Level  of  the  Land.  —  Slow  wearing  away  ;  movements 
of  the  crust;  cause;  proofs, — from  rocks,  from  present  changes;  in- 
stances ;  two  classes  of  movements ;  effect  on  continents. 

20.  Disturbance  of  the  Strata.  —  Original  position  ;  position  in  plains; 
in  mountains  ;  fault;  anticline;  syncline ;  dip;  monocline;  unsymmetri- 
cal  fold  ;  overturned  fold ;  crumpling  ;  joint  planes  ;  importance. 

21.  Agents  of  Weathering.  —  Agents  at  work ;  nature  of  process ;  result. 

22.  Work  of  Underground  Water.  —  Entrance  of  water  ;  proof  of  its 
presence, — wells,  plant  roots,  springs  ;  solution;  substances  aiding  solu- 
tion; changes  in  minerals  ;  result ;  plant  food;  frost  action. 

23.  Influence  of  Air  in  Weathering.  —  Heat  and  cold ;  effect  of  oxygen 
and  carbon  dioxide. 

24.  Organisms  as  Agents  of  Weathering.  —  (a)  Plants :  mechanical  work 
of  roots  ;  removal  of  mineral  substances ;  aid  to  underground  water. 
(b)   Animals:  kinds;  work  done ;  earthworms. 

25.  Rate  of  Weathering. — Illustrations  of  differences  in  rate  ;  effect 
of  rock  ;  of  climate,  —  arid,  damp,  cold,  warm  and  damp  ;  of  exposure, — ■ 
gentle  slopes,  steep  slopes  ;  slowness  of  weathering. 

26.  Results  of  Weathering.  —  Residual  soil;  other  soils;  dissolved 
mineral  substances ;  talus ;  avalanches ;  supply  of  tools  to  streams ;  for- 
mation of  sedimentary  strata ;  valley  broadening  ;  rock  sculpturing. 

27.  The  Agents  of  Erosion.  —  Winds;  rivers;  ocean;  lakes;   glaciers. 

28.  Denudation.  —  Definition;  tendency;  effect  of  uplift. 

29.  Age  of  the  Earth.  —  Probable  age  ;  reasons  for  belief ;  illustrations ; 
importance  of  grasping  the  conception. 

Questions.  — 17.  What  land  forms  are  seen  on  a  journey  from  Phila- 
delphia to  Chicago?     What  relation  between  land  forms  and  industries? 

18.  What  are  the  three  divisions  of  rocks?  (A)  How  are  rock  frag- 
ments assorted  by  water?  What  is  the  meaning  of  the  terms  strata, 
stratum,  and  stratified?  How  are  stratified  rocks  consolidated ?  (B)  In 
what  conditions  are  igneous  rocks  accumulated  on  the  surface?  De- 
sci-ibe  three  kinds  of  igneous  intrusions.  (C)  What  is  the  nature  of 
rnetamorphisra,  and  its  results?  Why  is  it  so  common  in  mountains? 
(D)  How  do  minerals  vary  in  durability  ?  What  two  conditions  influ- 
ence the  rate  of  rock  disintegration  ?  What  effect  has  this  on  the  form 
of  the  land  ? 

19.  What  changes  are  in  progress  on  the  earth's  surface?  What  evi- 
dences are  there  of  past  and  present  changes  of  level  ?  What  is  the 
nature  of  these  movements?    What  effect  has  this  on  the  continents? 


48  NEW  PHYSICAL   GEOGBAPHT, 

20.  Why  are  the  strata  of  plains  commonly  horizontal?  What  is  the 
condition  in  mountains?  Define  fault;  anticline;  synciine;  dip;  mono- 
cline. Draw  diagrams  to  illustrate  symmetrical,  un symmetrical,  and  over- 
turned folds.     What  are  joint  j)lanes?     Of  what  impo»'taiice  are  they? 

21.  AVhat  are  the  agents  of  weathering  and  how  do  they  work? 

22.  How  does  underground  water  enter  the  rock='V  What  proofs  are 
there  of  its  presence?  In  what  two  ways  does  it  work  chemically  in  dis- 
integrating the  rocks?     How  does  it  work  mechanically? 

23.  In  what  ways  is  the  air  effective  as  an  age-  tof  weathering? 

24.  In  what  ways  do  plants  aid  in  weathering  *     Animals  ? 

25.  Give  illustrations  of  differences  in  rate  of  J^reathering.  State  the 
three  chief  causes  for  differences.     What  effect  has  exposure  ? 

26.  How  is  residual  soil  formed  ?  What  other  kinds  of  soil  are  there  ^ 
State  the  other  effects  of  weathering. 

27.  AVhat  work  is  accomplished  by  the  agents  of  erosion? 

28.  What  is  denudation  ?     How  is  it  opposed  ? 

29.  What  evidence  is  there  that  the  age  of  the  earth  is  great? 
Suggestions.  —  (1)  Imitate   sedimentation  in  a   glass   dish.     Place 

sand,  pebbles,  and  clay  in  the  dish  with  water.  Stir  vigorously  and  let  it 
settle.  Sprinkle  on  the  water  a  handful  of  sand,  clay,  and  pebbles.  (This 
experiment  may  be  made  even  more  effective  if  a  mixture  of  sand,  peb- 
bles, and  clay  is  made  to  represent  land,  then  washed  with  a  sprinkling 
pot  into  a  glass  aquarium  partly  filled  with  water.)  Where  does  the 
finest  material  settle  ?  Are  the  layers  horizontal  ?  Vary  the  rate  of 
washing  and  observe  what  happens.  (2)  Even  if  the  rocks  and  miner- 
als in  Appendix  C  are  not  studied,  specimens  of  quartz,  feldspar,  calcite, 
sandstone,  limestone,  granite,  and  marble  should  be  studied.  The  last 
four  can  be  obtained  readily,  probably  in  a  stone  yard.  The  three  min- 
erals may  be  purchased  from  a  mineral  dealer  for  a  very  small  sum.  Do 
not  get  valuable  specimens,  but  buy  by  the  pound  and  break  it  up  for 
class  use.  Study  the  characteristics  mentioned  in  the  Appendix.  (3)  Are 
the  rocks  of  your  neighborhood  horizontal  or  tilted?  If  the  latter,  can 
you  find  folds  or  faults?  Describe  what  you  find.  Look  for  joint 
planes  and  study  them  ;  take  their  direction  with  a  compass ;  does  water 
escape  from  them?  Are  there  any  quarries  in  which  they  are  of  use? 
(4)  Find  specimens  of  rock  in  the  fields,  or  elsewhere,  showing  weather- 
ing. What  signs  of  weathering  do  you  find?  Are  there  red  or  yellow 
stains?  What  causes  them?  (5)  To  prove  that  water  expands  on 
freezing,  fill  a  bottle  with  water  and  freeze  it.  Even  a  toy  cannon, 
plugged  tightly,  would  break.  (6)  Place  a  thin  piece  of  stone  in  a 
fire.  Does  it  crack?  Heat  another  small  piece  slowly,  then  cool  it 
quickly  by  placing  it  in  cold  water.    These  experiments  illustrate  tUe 


CHANGES  IN  THE  EARTH'S   CRUST.  49 

expansion  with  heat  and  contraction  with  cold,  though  of  course  in 
nature  the  changes  are  not  so  great  as  this.  (7)  Look  for  illustra- 
tions of  roots  prying  rocks  apart.  This  may  best  be  seen  on  cliffs 
where  trees  are  growing.  Tell  what  you  see.  (8)  Watch  the  earth- 
worms. The  "  casts  "  left  when  they  are  driven  out  of  the  swollen 
ground  after  a  heavy  rain  are  made  of  earth  from  their  stomachs.  What 
evidence  do  you  find  that  earthworms  help  in  weathering  ?  Darwin  con- 
sidered them  of  enough  imj)ortance  to  write  a  book  on  them.  (9)  If  you 
live  in  a  glaciated  country  (Fig.  270),  look  for  glacial  scratches  recently 
uncovered.  Are  they  fresh?  Why?  Look  for  others  uncovered  for  a 
longer  time.  Are  they  fresh?  Why?  (10)  Study  the  soil  of  your 
vicinity  carefully  and  tell  its  characteristics.  (11)  If  you  can  find  a  cliff, 
look  for  a  talus  slope.  Of  what  is  it  made  ?  Are  the  fragments  angular  or 
round  ?  Are  they  all  of  the  same  kind  of  rock  as  the  cliff  ?  Have  any 
fragments  been  removed  by  water?  Have  any  fallen  recently?  Go  there 
in  spring,  when  the  frost  is  coming  out  of  the  ground,  and  see  if  there 
have  been  recent  falls.  (12)  If  the  water  of  your  vicinity  is  hard, 
find  out  if  mineral  is  deposited  in  tea  kettles  or  in  engine  boilers.  Per- 
haps the  teacher  of  chemistry  may  suggest  a  way  of  proving  that  there  is 
mineral  in  the  water.  (13)  Are  any  of  the  streams  that  you  know  receiv 
ing  rock  waste  from  the  valley  sides?  When  does  most  come?  Watch 
the  streams  to  see.  Does  this  sediment  prove  that  denudation  is  now  in 
progress?  Would  much  change  take  place  in  a  year?  In  a  century?  In 
a  million  years?     Think  of  this  carefully. 

Reference  Books. — Lyell,  Principles  of  Geology,  2  vols.,  Appleton, 
New  York,  1877  (out  of  print),  »|8.00;  Geikie,  Text-hook  of  Geology, 
Macmillan  Co.,  New  York,  4th  edition,  1903,  $10.00 ;  Dana,  Manual  of 
Geology,  American  Book  Co.,  New  York,  1895,  $5.00  ;  Leconte,  Elements 
of  Geology,  Appleton  &  Co.,  New  York,  1903,  $4.00 ;  Tarr,  Elementary 
Geology,  Macmillan  Co.,  New  York,  1902,  $1.40;  Scott,  Introduction 
to  Geology,  Macmillan  Co.,  New  York,  1902,  $1.90;  Geikie,  C7a.ss  Book 
of  Geology,  Macmillan  Co.,  New  York,  1886,  $1.10;  Brigham,  Textbook 
of  Geology,  Appleton  &  Co.,  New  York,  1901,  $1.40;  [Merrill,  Rocksy 
Rock  Weathering,  and  Soils,  Macmillan  Co.,  New  York,  1897,  $4.00 ; 
Shaler,  Origin  and  Nature  of  Soils  (p.  219),  12th  Annual,  U.  S.  Geological 
Survey,  Washington,  D.C- 


B 


CHAPTER   IV. 

RIVERS   AND   RIVER   VALLEYS. 

30.  Supply  of  Water.  —  Part  of  the  rain  water  returns  to 
the  air  by  evaporation,  part  sinks  into  the  ground,  and  part 
runs  off.  That  portion  which  passes  back  to  the  air  need 
not  be  considered  here.  Most  of  that  which  sinks  into  the 
ground  (p.  39),  eventually  returns  to  the  surface  by  slow 
seepage  and  from  springs.  It  may  continue  for  months  on  its 
slow  underground  journey  before  finding  conditions  that 
favor  its  return  to  the  surface.  Were  it  not  for  this  steady 
source  of  supply,  after  each  rain  rivers  would  quickly  dry  up. 
Then  river  navigation  would  be  stopped,  river  water  power 
would  frequently  fail,  and  the  water  supply  of  many  cities 
would  be  cut  off  for  a  large  part  of  the  time. 

From  a  third  to  a  fourth  of  the  rain  water  runs  off  at  the 
surface.  Therefore  every  rain  swells  the  volume  of  the 
streams,  adding  greatly  to  the  steady  supply  from  under- 
ground. When  the  snow  melts  or  the  rains  are  heavy,  the 
rivers  i^iay  be  quiokly  transformed  to  raging  torrents  (Figs. 
60,  61). 

The  presence  of  the  forest  tends  to  reduce  floods.  Its  dense 
undergrowth,  the  mat' of  decayiug  vegetation,  and  the  tangle  of 
roots  seriously  interfere  with  the  run  off  of  the  water.  There  is 
a  greater  run  off  (1)  during  heavy  rains  than  during  long,  slow 
drizzles ;  (2)  on  clay  soils  than  on  sandy  soils  ;  (3)  ou  frozen 
soils  than  on  those  with  no  frost. 

Some  rivers  have  their  water  supply  regulated.  This  is  true  of 
those  whose  supply  comes  chiefly  from  large  and  copious  springs 
(p.  59).  Lakes  act  as  reguhating  reservoirs,  out  of  which  streams 
flow  with  little  change  in  volume ;  thus  the  volume  of  Niagara  is 
almost  always  the  same.     Swamps  also  help  to  regulate  the  water 

60 


Fig,  60.  —  A  waterfall  in  a  dry  summer,  when  even  the  underground  supply  was 
limited  (a  part  of  the  water  has  been  led  off  for  use  in  a  mill). 


K 

m 

i 

dJ^^hI 

■ 

■ 

1 

^HIB 

W^^k 

M'- 

^^1 

^^M 

■■ 

^^d' 

8*9 

.1 

*i 

• 

.1 

#• 

■ 

m 

'km. 

-3 

1 

J 

Fig.  61.  —  The  same  as  Fig.  60  after  a  heavy  rain. 


Fig.  62.  —  A  rain-sculptured  earth 
column  in  the  Tyrol  of  Austria. 
The  bowlder  which  caps  it  helps 
to  protect  the  clay  beneath. 


Fig.  63. —  A  rain-sculptured  column  in  a 
clay  cliff  on  the  shore  of  Lake  On- 
tario, in  New  York. 


Fia  6i.i^  A  view  2-2  the  Bad  Lands  of  South  Dakota,  where,  aa  far  as  one  can 

see,  the  surface  is  rain-soulptured. 


RIVERS  AND  RIVER   VALLEYS.  51 

supply.     Glaciers  regulate  the  flow  of  many  mountain  streams ; 
but  the  melting  in  summer  greatly  increases  their  volume. 

Summary.  —  Underground  water  gives  to  streams  a  steady  sxijpply  ; 
the  rains  and  melting  snows  increase  their  volume.  TJie  forest,  yiature 
of  the  rain,  soils,  and  frost  influence  the  run  off.  Springs^  lakesj 
swamps,  and  glaciers  tend  to  regulate  the  volume  of  rivers. 

31.  Rain  Sculpturing.  —  The  surface  of  a  road  or  a  plowed  field 
is  often  gullied  by  the  washing  action  of  rains  and  rain-born 
rills.  The  material  removed  is  carried  on  toward  the  larger 
streams.  In  moist  countries  (Figs.  62,  63)  this  rain  sculpturing  is 
not  usually  so  noticeable  as  in  arid  regions  where  there  is  little 
vegetation  to  protect  the  soil.  Loose  clayey  soils  are  deeply  gul- 
lied by  the  occasional  heavy  rains  of  arid  regions  ;  but  there  is  so 
little  weathering  that  the  steep  slopes  are  not  greatly  rounded. 
Such  rain-sculptured  lands  are  known  as  Bad  Lands,  one  of  the 
largest  sections  being  in  South  Dakota  (Fig.  64).  They  are  unfit 
for  agriculture,  and  even  for- cattle  raising.  Where  the  forest  has 
been  cleared  for  centuries,  as  in  parts  of  Greece  and  Italy,  rain 
sculpturing  has  destroyed  much  farm  land. 

Summary.  —  In  arid  lands,  and  ivhere  the  forest  has  been  removed, 
the  land  is  sometimes  so  gullied  by  rain  sculpturing  as  to  unfit  it  for 
agriculture.     In  the  West  such  regions  are  known  as  Bad  Lands. 

32.  The  Rock  Load  of  Rivers.  —  To  the  mineral  ]oad  which 
is  brought  in  solution  by  underground  water  (p.  39)  is  added 
some  which  the  river  water  dissolves  from  its  bed.  This 
dissolved  load  is  sometimes  very  noticeable,  as  when  river 
water  is  "hard,"  or,  as  in  southwestern  United  States,  even, 
salt  or  alkaline. 

Fragments  of  rock,  loosened  by  weathering  (Figs.  57,  66), 
or  washed  in  by  the  rain,  are  also  carried  by  rivers.  Water 
buoys  up  these  suspended  rock  fragments  so  that  they  lose 
about  one  third  of  their  weight.  A  current  moving  at  the 
rate  of  one  and  a  half  or  two  miles  an  hour,  that  is  about  half 
as  fast  as  a  man  walks,  will  transport  small  pebbles;  one 
moving  a  quarter  of  a  raile  an  hour  carries  only  clay.     Iq 


52 


NEW  PHYSICAL   GEOGRAPHY. 


i!. 


''\7. 


a 

i 

en 

I— I 

u 


O 
-a 

«— I 

u 

3 


O 

CO 

a 

be 


3 
O 


CO 

6 


mountain  torrents  bowlders  weighing  hundreds 
of  pounds  are  swept  along  ;  but  only  sand  and 
clay  can  be  moved  over  level  lowlands. 

These  rock  fragments  are  used  as  tools  of 
erosion.  The  grinding  of  pebbles  together 
rounds  them  and  gradually  wears  them  down 
to  sand  and  clay ;  and  the  river  bed  is  also 
worn  away,  or  eroded,  by  the  grinding  of  these 
fragments  against  it. 

The  load  which  rivers  bear  may  be  judged  from 
the  following.  The  Mississippi  River  annually 
carries  to  the  sea  7,500,000,000  cubic  feet  of  sedi- 
ment. This  would  make  a  prism  one  mile  square 
at  the  base  and  268  feet  high.  It  also  carries 
2,850,000,000  cubic  feet  of  mineral  matter  in  solu- 
tion. Other  rivers  are  bearing  similar  loads. 
From  this  it  is  evident  that  rivers  are  perform- 
ing a  great  task  in  removing  rock  waste  from  the 
lands. 

Summary.  —  Rivers  hear  great  loads  of  minerals 
in  solution;  also  rock  fragments,  ivhose  size  varies 
ivith  the  velocity  of  the  currents.  Tliese  are  used 
as  tools  of  erosion. 

33.    Erosive  Work  of  Rivers.  —  Rivers  aid  in 

lowering  the  land  by  removing  the  materials 
supplied  by  weathering  and  by  rain  wash. 
At  some  time  in  their  history  most  of  them 
are  also  at  work  in  a  vigorous  attack  on 
their  channels.  This  work  is  both  chemical 
(corrosive)  and  mechanical  (corrasive),  and  it 
results  in  the  formation  of  river  valleys. 

Streams  cut  their  banks  (Figs.  69,  70)  as 
well  as  their  beds.  This  lateral  cutting  causes 
the  valley  to  be  broader  than  the  river  itself 
(Figs.  6o,  67).     This  is  especially  true  where 


Fig.  66.  —  The  Gunnison  River,  Colorado.  Rock  fragments  from  the  cliffs  have 
made  a  talus,  which,  sliding  into  the  river,  supplies  it  with  tools  for  work 
(see  also  Fig.  57) .  A  railway  follows  this  narrow  valley,  one  of  its  bridges 
being  seen  in  the  distance.  To  pass  along  this  gorge  it  has  to  wind  about, 
crossing  the  stream  by  bridges  and  tunneling  the  rocks. 


Fig.  f;7.— a  narrow  gorge  (Enfield)  in  central  New  York.  One  wall  of  a  pot 
hole  is  seen  in  the  foreground  on  the  left.  The  stream  course  is  here  guided 
hy  two  joint  planes  which  cause  the  smooth,  straight  walls  hetweeu  which 
the  water  is  flowing. 


Fig.  68.  —  Ice  iu  the  same  fall  as  Figs.  60  and  61. 


Fig.  69.  —  A  stream  swinging  against  and  undercutting  a  shale  cliff,  showing 
lateral  ercsion  in  a  gorge  where  the  stream  is' also  rapidly  deepening  its  bed. 


Fig.  70.  —  Lateral  swinging  of  a  stream  against  a  clay  bank,  which  is  caused  to 
slide  into  the  stream.     In  this  way  the  valley  is  being  broadened. 


Fig.  71.  — Watkins  Glen  in   central   New  York.     A  small  stream   is  cutting 
this  gorge  deeper.    It  is  a  succession  of  rapids  and  cascades,  at  the  base  of 
which  pot  holes  are  being  cut  in  the  shale.    One  fairly  large  pot  hole  appears 
D  the  near  foreground ;  others  are  seen  farther  upstream. 


RIVERS  AND  RIVER    VALLEYS.  53 

the  river  swings  against  loose  material  which  slides  into  the 
stream  (Fig.  70). 

The  rate  of  valley  deepening  varies  greatly  according  to 
the  rock,  the  slope,  and  the  volume.  A  stream  naturally  cuts 
faster  in  soft  than  in  hard  rock  ;  on  steep  slopes  than  on 
gentle  slopes  ;  with  great  volume  than  witii  small  volume. 
The  effect  of  difference  in  volume  may  be  seen  in  many 
streams,  wliich  at  ordinary  times  do  little  work  of  erosion, 
but  when  in  flood  become  powerful  erosive  agents  (Fig.  61). 

Since  sediment  supplies  rivers  with  cutting  tools,  this  also 
has  an  important  effect  on  river  erosion.  When  there  is  little 
sediment,  erosion  is  greatly  reduced.  For  example,  Niagara 
River  emerges  from  Lake  Erie  as  clear  water,  the  sediment 
having  been  deposited  in  the  lake.  Therefore,  down  to  the 
Falls,  the  river  has  been  able  to  do  very  little  toward  cutting 
a  valley  (Fig.  483).  The  Colorado  River,  on  the  other  hand, 
with  a  heavy  load  of  sediment,  has  cut  an  enormous  canyon 
(Figs.  1,  477),  which  it  is  still  rapidly  deepening. 

Other  rivers,  like  the  lower  Mississippi,  have  more  sedi- 
ment than  they  can  carry,  and  must  deposit  some  of  it,  build- 
ing up  their  beds.  Rivers  tliat  are  deepening  their  valleys 
are  said  to  be  degrading  (Fig.  71),  those  that  are  building 
up  their  beds  are  aggrading  their  valleys  (Fig.  112). 

Joint  planes  also  influence  the  rate  of  erosion,  and  sometimes 
direct  the  course  of  a  stream  (Fig.  67).  Ice  (Fig.  68)  is  like- 
wise of  importance.  In  winter  it  diminishes  the  supply  of  water ; 
but  in  spring  its  melting  adds  to  the  floods ;  and  it  pries  and 
breaks  off  fragments  of  the  rock  and  carries  them  along. 

Summary.  —  Rivers  cut  vertically  on  their  beds,  and  laterally  at 
their  banks,  the  rate  varyinr/  icith  the  rock,  slope,  volume,  and  sediment 
supply.  Some  ricers  are  aggrading,  others  degrading,  their  valleys. 
Joint  planes  and  ice  also  iuftaence  river  ivork. 

34.  Waterfalls.  —  When  a  stream  is  degrading  its  bed,  con- 
ditions are  often  discovered  which  cause  the    formation  of 


64  NEW  PHYSICAL   GEOGRAPHY. 

rapids  and  falls.  Most  commonly  it  is  a  difference  in  hard- 
ness of  the  strata.  Soft  rocks  are  cut  more  rapidly  than  hard, 
and  therefore  rapids  and  falls  occur  where  a  degrading 
stream  flows  from  a  hard  to  a  soft  layer.  Such  falls  are 
very  common  in  regions  of  horizontal  strata,  where  hard 
layers  (Fig.  72)  retard  erosion  while  weaker  layers  beneath 
are  removed.  This  undermines  the  hard  layer,  and  when  a 
piece  breaks  off,  the  fall  retreats  upstream  (Fig.  75),  always 
being  located  on  the  steep  edge  of  the  hard  stratum  (Fig. 
74).  There  are  thousands  of  illustrations  of  this,  of  which 
Niagara,  located  on  a  hard  layer  of  limestone  (Fig.  482),  is 
the  largest  and  best. 

Falls  and  rapids  cause  streams  to  concentrate  their  energy  in 
spots.  This  is  well  illustrated  by  Niagara,  where  the  falling 
water  has  .excavated  a  deep  hole  at  the  base  of  the  fall.  Similar 
holes,  called  pot  holes  (Figs.  67,  71,  73),  are  common  in  streams  that 
are  degrading  their  beds.  They  are  enlarged  and  deepened  by 
the  whirl  of  water,  which  carries  pebbles  about  with  it.  Pot-hole 
work  is  an  important  factor  in  the  excavation  of  valleys. 

Waterfalls  and  rapids  are  of  great  importance  in  supplying 
power,  the  water  being  led  through  canals  or  pipes  and  allowed 
to  fall  upon  a  wheel  which  turns  machinery.  Now  that  elec- 
tricity is  used  for  power,  falls  are  of  value  even  in  sparsely 
settled  regions.  Niagara  Falls  power,  transmitted  by  wire,  lights 
and  runs  the  cars  of  Buffalo ;  falls  in  the  Alps  and  Sierra  Nevada 
supply  electric  power  for  places  miles  away. 

Summary.  — Falls  and  rapids,  of  use  for  icater  poioer,  are  common 
where  a  degrading  stream  Jlows  from  a  hard  to  a  soft  stratum,  as  at 
Niagara.     Pot  holes  are  excavated  by  the  falling  water. 

LIFE    HISTORY   OF   A   RIVER   VALLEY 

A  river  valley,  like  an  animal  or  plant,  changes  as  it  grows 
older.  To  understand  these  changes,  or  the  life  history  of 
a  river,  it  seems  best  to  start  with  simple  conditions  —  a 
plain  of  moderate  elevation,  with  nearly  horizontal  strata, 


Fig.  72.  —  A  hard  layer  of  rock  in  a  stream 
bed.  When  the  water  is  higher  there 
is  a  fall  here,  and  the  falling  water 
removes  the  softer  layer  from  beneath, 
undermining  the  hard  stratum. 


Fig.  73.  —  The  man  is  standing  in 
a  pot  hole.  In  the  bottom 
there  are  small  round  stones 
which  the  water  whirls  about, 
grinding  out  the  rock  and  thus 
deepening  and  enlarging  the 
hole. 


Fig.  74.— Two  diagrams  to  illustrate  the  history  of  a  waterfall.  In  the 
left  hand  figure  a  hard  stratum  (the  darkest)  has  a  waterfall  (W)  over.its 
edge.  As  the  falling  water  undermines  this  hard  stratum  the  fall  re- 
treats upstream,  always  being  located  on  the  hard  layer.  At  a  later 
stage,  therefore  (right  hand  figure),  the  fall  is  farther  upstream ;  and  falls 
are  also  present  on  the  same  layer  in  two  tributaries.  The  stream  ero- 
sion has  formed  a  deep  gorge  below  the  fall,  as  in  the  case  of  Niagara. 


Fig.  75.  —  Taugnanuock  Falls  near  Ithaca,  New  York,  220  feet  high.  The  angles 
and  smooth  rock  faces  near  the  upper  part,  and  the  angle  in  the  crest  of  the 
fall,  are  caused  by  Joint  planes.  A  few  years  ago  a  huge  block  fell  from  the 
crest  of  the  fall,  giving  its  present  shape;  before  that,  the  crest  of  the  faU 
jM"ojected  downstream. 


RIVERS  AND  RIVER   VALLEYS. 


55 


and  a  moist  climate.  Later  study  will  show  that  many  rivers 
depart  from  such  an  ideally  simple  condition  ;  but  these 
variations  will  be  better  understood  if  we  first  study  a 
simple  case.  Such  a  study  will  reveal  some  important  laws 
of  valley  formation. 

35.  Young  Stream  Valleys.  —  On  such  a  plain  as  that 
JQst  described  the  drainage  is  at  first  somewhat  indefinite. 
Water  fills  the  de- 
pressions in  the 
plain,  forming  shal- 
low lakes  ;  and  large 
expanses  of  the  level 
plain  form  flat- 
topped  divides, 
often  swampy,  be- 
cause there  has  not 
been  time  enough 
for  many  tributaries 
to  develop.  Wher- 
ever water  runs  off, 

it  flows  in  consequence  of  the  original  slope,  or  has  a  conse- 
quent course.  Florida  (Figs.  78,  79)  has  such  a  condition  of 
drainage. 

The  consequent  streams  quickly  cut  into  the  plain,  forming 
narrow,  steep-sided  valleys  (Fig.  76).  As  they  degrade  along 
their  beds  they  discover  differences  in  hardness  of  the  strata, 
and  therefore  develop  falls  (Fig.  74)  and  rapids.  At  the  same 
time  weathering  and  meandering  slightly  widen  the  valley. 

There  is  a  limit  below  wdiich  no  part  of  a  stream  may 
deepen  its  bed,  and  this  is  called  its  base  level  (Fig.  81).  The 
sea  is  the  permanent  base  level,  and  the  down-cutting  of  every 
stream  that  enters  the  sea  is  arrested  by  it.  Lakes  act  as 
temporary  base  levels  ;  but  their  effect  does  not  last  long, 
because  the  sediment  that  the  streams  bring,  quickly  fills  and 
destroys  them  (p.  164). 


Fig,  7o.  —  A  young  stream  valley  on  a  plain.  It  is 
still  well  above  base  level  ;  tbe  divides  are  flat- 
topped  ;  there  are  few  tributaries ;  and  lakes  still 
exist. 


56  NEW  PHYSICAL   GEOGRAPHY. 

While  the  lakes  are  being  filled  and  the  valleys  deepened, 
tributaries  are  developing.  Little  by  little  the  tributary 
streams  gnaw  their  way  back  from  the  main  stream,  narrow- 
ing the  flat-topped  divides  and  in  time  draining  the  level, 
swampy  areas. 

A  stream  with  these  characteristics  —  steep-sided  valleys, 
waterfalls,  lakes,  illy  defined  divides,  and  tributaries  only 
partly  developed  —  is  a  young  stream.  It  has  not  had  long 
to  work,  and  consequently  its  valley  is  not  thoroughly 
developed  ;  it  is  still  growing.  A  young  stream  is  better 
developed  in  its  lower  portion  than  above,  as  a  young  tree 
has  a  thick,  strong  trunk  and  delicate,  growing  branches. 
The  Niagara  Gorge  (Fig.  483)  and  Colorado  Canyon  (Fig. 
1)  are  good  examples  of  young  stream  valleys  (see  also 
Figs.  77,  80)  ;  but  no  lakes  remain  in  the  course  of  the 
Colorado. 

Although  such  valleys  are  young,  the  time  reqidred  to  perform 
even  this  much  work  is  long,  measured  in  years.  A  river  may  have 
been  working  for  5000  or  even  50,000  years,  and  yet  have  a  valley 
with  the  characteristics  of  youth.  As  in  the  case  of  plants,  some 
of  which  grow  old  in  a  few  days  while  others  require  weeks  or 
even  years,  so  in  river  valleys  there  is  a  great  difference,  under  dif> 
ferent  circumstances,  in  the  time  required  to  pass  the  stage  of  youth. 
Yet  in  all  cases  the  features  of  youth  are  so  distinct  that  a  young 
valley  is  hardly  more  difficult  to  distinguish  than  a  young  plant. 

Summary. — A  young  river  is  one  that  has  not  had  a  long  time 
for  development.  It,  therefore,  has  a  steep-sided  valley,  feiv  tributa- 
ries, indefinite  divides,  and,  if  conditions  favor,  waterfalls  and  lakes. 
TJie  term  "  youth  "  does  7iot  refer  to  years,  but,  as  in  plants,  to  form.  • 

36.  The  Grade  of  a  Stream. — The  lowest  grade  to  which 
a  stream  can  cut  its  channel  is  one  down  which  it  is  just  able 
to  carry  its  sediment  load.  The  grade  line  is  a  curve,  reach- 
ing base  level  at  the  river  mouth  and  rising  rapidly  near  the 
divide  (Fig.  81).  All  streams  that  have  not  reached  grade 
are  working  toward  it,  and  young  streams,  which  have  a 


Fig.  77.  — Narrow  Rorge  of  a  young  stream  cut  in  hard  rock.  Even  here  the 
valley  has  been  widened  somewhat  by  measoering  and  by  weathering. 
The  latter  cause  accounts  for  the  breadth  of  tii«  gorge  at  the  top. 


Fig.  78.  —  Map  of  a  part  of  the  Florida  plain  where  the  swamps  (indicated  by  **) 
and  lakes  have  not  yet  been  drained  by  the  young  streams  (see  Fig.  79),    The 
lines  are  contour  lines.    The  meaning  of  these  is  explained   in  Appendix  T 
(Part  of  Citra,  Fla..  Topographic  Sheet.  U.  S.  Geologicul  Survey.) 


pn^^Hnmii.i  *uj|»*  u.i  41 


■iwi  II  ,.jiwjinii.iijuii,iiii.ijpii.jii^-iiii  mniy-iii  nii.HnifBtii  mjwHjju.iiiij  «m|ijp|| 


Pjq,  79.  _  a  ttat-copped,  swampy  divide  in  tlie  Florida  plain,  on  which  the 
drainage  is  so  young  that  the  tributary  streams  have  not  had  time  to 
gnaw  back  and  narrow  the  divide  so  as  to  drain  the  swamps  (see  Fig.  78). 


Fig.  80.  —  A  young  valley  (on  the  right  of  the  center)  cut  in  soft  material. 
The  sliding  down  of  the  sides  has  broadened  this  valley.  (Contrast  with 
Fig.  77  in  hard  rock.) 


wM?MMmmM^mMMm/j//Mm///M>/^?;f^ 


Fig.  81.  —  Diagram  to  illnstvnt'^"  *\f^  m'^am'iig  of  giuiie  uii-J  base  level. 


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RIVERS  AND  RIVER   VALLEYS. 


57 


steeper  slope  than  necessary,  are  actively  degrading  their  beds 
toward  grade.  It  often  happens,  however,  that  a  stream  has 
too  gentle  a  grade  to  move  its  sediment  load  over.  Then, 
to  secure  a  steeper  grade,  deposit  is  made.  Most  streams  on 
broad  floodplains  are  thus  aggrading  their  valleys. 

Summary.  —  77^6  grade  of  a  stream  is  the  lowest  slope  over  which 
the  water  can  move  its  sediment  load.  Young  streams  are  degrading 
their  valleys  toward  this  grade;  hut  many  streams  are  engaged  in 
aggrading  their  course  to  secure  a  steeper  grade. 

37.  Mature  Valleys.  —  When  grade  is  reached  by  a  river, 
further  down-cutting  ceases;  but  weathering  of  the  valley 
sides  continues. 
This  slowly  broad- 
ens the  valley, 
wearing  the  sides 
back  and  making 
the  slopes  less  steep 
(Figs. '83,  85,  86). 
The  broadening  of 
the  valley  is  first  accomplished  near  the  mouth ;  but  it 
slowly  extends  upstream.  Young  streams  exist  for  a  long 
time  among  the  headwaters,  as  young  twigs  appear  on  the 
outer  branches  of  even  an  old  tree. 

In  a  mature  stream,  grade  has  been  reached  throughout 
most  of  its  course,  and  any  lakes  that  may  have  existed  have 
long  since  been  filled.  Nor  can  there  be  waterfalls,  because 
the  graded  stream  is  no  longer  cutting  into  the  rock. 

Tributaries  have  developed  in  such  numbers  that  the  di- 
vides have  become  well  defined,  and  all  water  that  falls  on 
the  land  finds  slopes  ready  for  it  to  flow  down  (Fig.  82). 
Again  the  comparison  may  be  made  to  a  tree,  which  at  first 
has  a  trunk  and  few  branches,  but,  as  it  grows  older,  develops 
an  increasing  number  of  minor  branches  and  twigs. 

By  the  development  of  so  many  tributaries  the  number  of 


Fig.  83.  —  To  illustrate  the  broadening  of  valleys 
from  youth  to  old  age. 


58 


NEW  PHYSICAL   GEOGRAPHY. 


slopes  and  the  amount  of  surface  exposed  to  weathering  are 
greatly  increased  (Fig.  84).  These  increasing  slopes  may 
supply  so  much  sediment  to  the  main  streams  that  they 
cannot  carry  it  all  to  the  sea.  They  then  begin  to  aggrade 
their   courses  to  establish  a  steeper  grade   down  which  to 

carry  the  sediment.  In 
doing  tliis  they  build 
floodplains  (p.  61). 


Summary.  —  A  valley 
loith  moderately  sloping 
sides,  a  fairly  icell  estab- 
lished grade,  no  lakes, 
waterfalls  or  rapids,  icell- 
defined  divides,  numerous 
tributaries,  and  floodplains 
in  its  lower  portion  is 
mature. 


Fig.  84. — To  illustrate  the  increase  in  slopes 
as  valleys  broaden.  The  line  A  A,  drawn 
on  the  level  surface  of  a  young  plain, 
gradually  lengthens  to  JS  £  as  the  val- 
leys broaden  to  maturity. 


38.  Old  Valleys.  —  As  valleys  grow  older,  the  slopes  become 
more  and  more  gentle  (Fig.  83)  until  the  surface  is  reduced  almost 
to  sea  level.  An  old  land  surface,  reduced  to  the  condition  of  a 
low,  rolling  surface,  is  called  a  peneplain  (almost  plain). 

Many  parts  of  the  continents  are  ancient  enough  to  have  become 
peneplains  ;  but  there  are  numerous  accidents  which  commonly 
interfere  with  this  result.  Of  these  accidents  the  most  important 
are  uplifts  of  the  land,  which  continually  give  to  streams  new 
tasks  to  perform.  Therefore,  few  valleys  have  passed  the  stage 
of  maturity. 

Summary.  —  Old  valleys  are  so  broad  that  the  surface  is  reduced 
almost  to  a  plain,  or  to  a  p)eneplain ;  but  uplift  of  the  land  is  so  fre- 
quent that  few  regions  have  reached  this  condition. 

39.  Importance  of  Valley  Form.  —  Young  valleys  encourage 
some  of  man's  activities  and  interfere  with  others.  The 
waterfalls  furnish  power;  and  the  lakes  are  valuable  for  navi- 
gation, for  their  influence  on  the  climate  of  neighboring  land, 
and  aii  sources  of  food-fish  and  ice.      On  the  other  hand,  land 


Fig.  85.— Railway  crossing  the  Appalachians  along  one  of  the  narrow,  winding 
mountain  valleys,  so  steep  that  the  forest  has  not  been  removed.  This 
valley  has  the  form  of  late  youth,  or  early  maturity. 


E>a.  86.  —  Thse  Connecticut,  at  Northampton,  Mass.;  a  broad,  mature  valley, 
with  geotty  sloping  sid*?^.  dotted  wkh  farms 


Fig.  87.  —  An  underground  river  in  Howe's  Cave,  New  York  (copyright,  Z'\:m 

by  S.  R.  Stoddard,  Glens  Falls,  N.Y.). 


Fia.  S^-'-Spnuy  wtiere  wa4;er  {tours  oui  tcota  a  Jimetttoae  cavern  iu  Iowa. 


RIVERS  AND  RIVER    VALLEYS.  59 

cut  by  young  valleys  is  difficult  to  cross,  the  valley  bottoms 
furnish  poor  grades  for  roads  and  railways  (Figs.  57,  66,  71, 
77),  and  much  of  the  country  is  unfitted  for  agriculture. 

In  contrast  to  young  valleys,  mature  valleys  are  the  seats 
of  agriculture,  and  their  fertile  floodplains  are  among  the 
best  farm  lands  of  the  world.  Travel  across  country  is  easy, 
and  the  river  valleys  are  important  highways  (Figs.  85,  86). 
Even  the  rivers  themselves,  if  large,  have  so  gentle  a  grade 
that  they  are  navigable.  Thus,  flourishing  farms  and  thriv- 
ing towns  and  cities  line  the  river  banks  and  dot  the  slopes  of 
mature  valleys.  This  is  well  illustrated  along  the  Mississippi 
valley,  which  offers  a  striking  contrast  to  the  young  Colorado 
valley  (Fig.  1). 

Summary. —  Yoimg  valleys  are  unfavorable  for  occupation;  hut 
mature  valleys  are  adapted  to  agriculture  and  dense  settlement, 

40.  Springs  and  Underground  Channels.  —  Where  condi- 
tions are  specially  favorable,  underground  water  (p.  39)  is 
led  back  to  the  surface,  appearing  as  a  spring.  Sometimes 
it  comes  out  along  a  porous,  sandy  layer,  sometimes  along  a 
joint  plane.  There  are  many  springs  along  rivers  ;  but  they 
occur  also  on  hillsides  and,  in  fact,  wherever  favorable  con- 
ditions direct  underground  water  to  the  surface. 

Some  large  and  permanent  springs  rise  from  deep  in  the 
ground  through  fault  planes,  often  bringing  heated  water  to 
the  surface.  Such  springs  often  have  so  much  mineral  in 
solution  that  they  are  known  as  mineral  springs,  and  have 
important  medicinal  properties.  The  Hot  Springs  of  Ar- 
kansas, and  the  mineral  springs  of  Saratoga,  Carlsbad,  and 
Vichy,  are  examples  of  such  springs. 

Water  percolating  through  soluble  rock,  like  limestone,  dis- 
solves the  rock  along  joint  planes  and  bedding  planes.  This 
often  results  in  the  formation  of  long,  irregular  underground 
valleys,  or  caverns,  like  that  of  Mammoth  Cave,  Ky.  In  such 
a  country  much  of  the  drainage  is  underground  (Fig.  87). 


60  NEW  PHYSICAL   GEOGRAPHY, 

There  are  large  surface  streams  with  few  tributaries,  the 
chief  water  supply  coming  from  the  springs  (Fig.  88)  that 
bring  the  cavern  water  to  the  surface. 

Entering  such  a  cavern,  one  passes  through  a  maze  of  dark, 
irregular  j^assages,  in  which  it  is  easy  to  lose  oneself.  From  the 
roof  hang  stalactites  (Figs.  87,  91)  of  carbonate  of  lime,  which  the 
water  dissolved  in  its  passage  through  the  limestone  rock  and 
deposited  on  emerging  into  the  cavern.  In  form  they  resemble 
icicles.  Stalagmites  (Fig.  91)  are  built  up  from  the  cavern  floor 
by  the  dripping  water,  as  ice  columns  are  formed  under  a  spout. 


eORMAY  &  CO.,    N.Y. 

Fig.  89. — To  illustrate  the  formation  of  limestone  caves.  Water  entering  the 
sink  holes  has  formed  great  vertical  cavities,  and  also  horizontal  caverns 
through  which  it  flows,  emerging  in  the  form  of  springs  near  the  natural 
bridge  on  the  right. 

Often  the  stalactites  and  stalagmites  unite  to  form  columns 
(Fig.  91),  and  sometimes,  as  in  the  Luray  Cave,  they  assume  weird 
and  even  beautiful  forms. 

The  surface  of  a  limestone  country  is  pitted  with  saucer-shaped 
depressions,  known  as  si7ik  holes  (Fig.  90).  Through  these  the 
water  drains  into  the  ground,  though  sometimes  the  entrance  into 
the  ground  is  clogged,  changing  the  sink  hole  to  a  pond.  Tliese 
sink  holes  are  caused  by  settling  of  the  ground,  due  to  solution  of 
the  rock  beneath  (Fig.  89). 

Weathering,  lowering  the  surface,  slowly  wears  away  the  cav- 
ern roofs.  Sometimes  only  a  small  part  of  the  roof  is  left,  span- 
ning the  valley  as  a  natural  bj^idge  (Fig.  92). 

Summary.  —  Springs  occur  inhere  conditions  direct  underground 
water  to  the  surface,  for  example,  a  p)orous  layer,  a  joint  plane, 
fault ]jlai)i  (many  hot  or  mineral  springs),  or  a  cavern  oxitlet.  Cav- 
erns occur  where  underground  water  dissolves  passageways  through 
soluble  rock  like   limestone.     The  water  enters  the  ground  through 


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Fia.  92.  — Natural  Bridge,  Virginia.    This  bridge  is  a  part  of  au  old  cavern 
roof,  the  remainder  having  been  removed  by  weathering. 


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Fia.  94.  —  A  small  ox-bow  curve  in  a  meadow  brook.  A  cut-off  has  been 
started,  but  brush  was  put  in  to  stop  it  from  (y^ntinuing.  (L.  O.  Towne, 
Haverhill,  Mass.,  Photographer.) 


YiG   95  —The  same  as  Fig.  94  with  the  rnt-off  coniiileted  in  spite  of  the 
br'^sb.     (L.  O.  Townt*,  Plavcrh'"'    '*l;t.s>;..  IMioto.-ranUeyJ 


RIVERS  AND  RIVER    VALLEYS. 


61 


sink  holes,  j^osscs*  along  an  underground  course,  and  emerges  as 
a  sjyring.  It  deposits  stalactites,  stalagmites,  and  columns  in  the 
caverns. 

41.  River  Floodplains.  —  Streams  are  often  bordered  by 
level  plains,  built  of  sediment  which  they  have  brought. 
Even  a  mountain 
torrent,  that  is  de- 
grading its  bed, 
may  have  narrow 
patches  of  such 
deposits  on  one  or 
both  sides.  Rivers 
that  are  aggrading 
their  courses  are 
alwaj'S  bordered 
by  such  alluvial 
plains,  or  flood- 
plains.  They  are 
usually  bordered 
by  bluffs  (Figs.  96, 

97,  102),  against  which  the  river  cuts  as  it  swings  over  the 
flood  plain.  These,  being  higher  and  drier  than  the  floodplain, 
are  often  selected  as  the  sites  for  towns  and  cities,  as  in  the 
case  of  Vicksburg  on  the  Mississippi. 

Broad  floodplains  are  due  to  the  fact  that  there  is  more 
sediment  than  can  be  carried  down  the  grade.  Therefore 
some  must  be  deposited.  When  such  rivers  rise  and  over- 
flow their  banks,  they  submerge  the  neighboring  lowland 
(Figs.  93,  99),  and,  with  each  flood,  deposit  a  layer  of  sedi- 
ment, as  mud  is  deposited  on  a  sidewalk  when  the  gutter 
overflows.  This  slowly  raises  the  level  of  the  floodplain  ; 
and,  since  it  is  being  built  by  a  broad  sheet  of  water,  its 
surface  is  made  fairly  level. 

Many  broad  floodplains,  like  that  of  the  Mississippi  (p.  327), 
are  very  fertile  ;  and  frequent  overfloAV,  by  bringing  new  soil. 


Fig.  96.  — Canadian  river,  Oklahoma.  Througii  this 
floodplain  the  river  sweeps  in  great  curves  be- 
tween bluffs  which  are  seeu  in  the  foreground 
and  in  the  far  distance. 


62 


NEW  PHYSICAL   GEOGRAPHY. 


helps  to  keep  them  so.  Their  levelness  and  dampness  further 
fit  them  for  agriculture.  In  many  arid  regions  the  river 
water  is  led  out  over  the  floodplains  for  the  purpose  of  irri- 
gation, and  in  some  arid  regions,  as  along  the  Nile,  the  over- 
flows themselves  take  the  place  of  rainfall. 

A  floodplain  is  usually  highest  near  the  river,  because  this 
part  is  most  frequently  reached  by  floods.  This  higher  portion 
is  known  as  the  natural  levee.  On  it  are  farms,  towns,  and  cities; 
for  example,  New  Orleans ;  but  behind  it  is  a  low,  swampy  tract, 
too  wet  for  habitation.     At  New   Orleans,   the   natural   levee  is 

only  a  few  feet  above  the  river 
level  and  the  swamp.  To  pro- 
tect the  towns  and  farms 
from  overflow,  men  build  still 
Ijigher  embankments,  or  levees, 
which  serve  to  hold  back  many 
of  the  floods.  When,  however, 
a  great  flood  breaks  through 
the  levee,  vast  areas  are  inun- 
dated, property  is  destroyed, 
and  lives  lost.  Along  the 
Mississippi,  such  a  break  is 
known  as  a  crevasse. 

No  river  flows  in  a  perfectly 
straight  line.  On  the  con- 
trary, irregularities  in  the  bed, 
and  other  causes,  turn  the  cur- 
rent toward  one  side,  and  cause 
the  stream  to  cut  first  at  one 
bank,  then  at  the  other  (Figs. 
70,  102).  This  starts  a  curv- 
ing or  swinging  of  the  river, 
known  as  a  meander  (Yig.  97), 
(Fig.  345)  whose  lower  course 
are   peculiarly    favorable   to 


Fig.  97. —  To  show  by  arrows  how,  in 
meanders,  a  river  current  cuts  against 
one  bank  and  deposits  on  the  other. 
The  bluffs  are  shown  on  the  two  sides 
of  the  floodplain. 


named  after  a  river  in  Asia  Minor 

is   very   meandering.     Floodplains 

the  development  of  meanders  because  of  the  low,  level  land  and 

the  loose  sediment,  which  is  easily  moved  by  the  water.     While 


73 
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Fig.  99.  —  The  Ohio  River  in  flood  near  Parkersburg,  West  Va.    Notice  that 
the  water  rises  to  the  first-story  windows. 


Fig.  100.  —  An  abandoned  ox-bow  curve  in        Fig.  101.  —  River   terraces   being 
the  Connecticut  valley  near  Northamp.  cut  by  a  degrading  stream  in 

ton,  Massachusetts.  the  Andes  of  Peru- 


RIVERS  AND  RIVER    VALLEYS, 


63 


the  stream  ^uts  on  one  bank  it  deposits  sediment  on  the  other 

(Figs.  97,  102),  and  thus  forms  a  broad,  sweeping  curve  known 

as  the  ox-bow  curve  (Fig.  98).     The  curves  vary  in  size  with  the 

volume  of  the  river  (Figs.  93,  98),  being  in  the  Mississippi  fully  five 

miles  in    diameter. 

As  the  meandering 

continues    it    often 

happens    that    the 

stream   cuts  across 

the  neck  of  a  curve 

and     abandons     it 


Fig.  102.  —  The  Missouri,  a  meandering  river  bordered 
by  floodplain,  and  cutting  at  the  base  of  its  bluffs, 
wherever  the  current  swings  against  them. 


(Figs.  94, 95).  The 
lake  thus  formed 
is  called  an  ox-boiv 
cut-off  (Fig.  100). 
Floodplains  have 
many  such  aban- 
doned meanders  in 
all  stages  of  de- 
struction by  filling.  On  the  Mississippi  floodplain  there  are 
places  where  the  river  course  has  been  shortened  fifteen  miles  by 
a  single  cut-off. 

Summary.  —  Large  jloodplaiiis  are  level  tracts  of  fertile  alluvial 
land  bordering  rivers.  They  are  bv.ilt  during  foods  by  the  deposit 
of  sediment,  and  are  usually  bordered  by  bluffs  cut  by  the  river. 
They  are  highest  near  the  river,  at  the  naturcd  levee,  on  which  artificial 
levees  are  built.  Over  the  foodplain  the  river  sivings  m  meander- 
curves,  sometimes  abandoning  them,  forming  ox-bow  cut-offs. 

42.  River  Terraces.  —  The  swinging  of  a  river  causes  it  to  be 
first  on  one  side  of  its  valley,  then  on  the  other.  If  it  is  degrading, 
it  cuts  downward,  now  in  one  place,  now  in  another.  This  leaves 
terraces,  or  narrow,  flat-topped  strips,  each  faced  by  a  steep  slope 
on  the  side  toward  the  stream  (Figs.  101,  103). 

If  an  unlift  elevates  a  floodplain  so  that  the  river  cuts  down  into 
it,  a  series  of  very  perfect  terraces  is  carved  in  the  soft  floodplain 
deposits.  During  the  removal  of  any  other  kind  of  soft  deposits, 
such  as  glacial  and  lake  deposits,  rivers  also  carve  perfect  terraces. 


64 


NEW  PHYSICAL   GEOGRAPHY, 


Kiver  terraces  are  often  excellent  farm  land.     The  soil  is  good; 
they  are  well  drained ;  the  surface  is  level ;  and,  in  ari'd  countries, 


i.1-'  jwji  I 


:>i«j«*v!<*?/'* 


Mcfiilcrrancnii      5'ea 


Fig.   103.  —  Three  stages  of  a  degrading  river,  to  illustrate  the  formation  of 

terraces.    Describe  these. 

irrigation  ditches  .a,re  easily  led  over  their  tops.     Some   of   the 
6est  farm  land  in  the  Connecticut  valley  is  terrace  land. 

Summary.  —  River  terraces  are  flat-topped  strips  of  land  ivith 
^teep  front,  bordering  rivers.  Tliey  are  formed  during  the  removal 
of  materials,  especially  soft  materials,  by  a  degrading  stream. 

43.    Deltas.  —  On  enteiing  tl:^e  sea  or  a  lake,  a  river  finds 

its  current  suddenly  checked. 
Some  of  its  sediment  is  re- 
moved bv  waves  and  cur- 
rents,  but  much  is  deposited 
in  the  quiet  water  near  its 
mouth,  building  up  land. 
To  this  land  the  name  delta 
is  applied,  because  of  the 
resemblance  to  the  Greek 
letter  delta  (A),  as  seen  in 
the  Nile  (Fig.  104). 

Deltas  have  the  triangular 
shape  because  a  single  chan- 
nel will  not  carry  all  the 
water  over  their  level  surface. 
For  this  reason  the  river 
divides  into  channels,  or  dis- 


/-/ /:)  \  \ 


DES/cnr 


DESCnT  ■    1 


m^ 


jl 


MMiMtetokawalMH 


Fig.   104. —The  delta  of  the  Nile.    The 
shaded  area  is  reachecj  by  floods. 


BIVERS  AND  RIVER    VALLEYS. 


65 


"^BATTLEDORE  l< 

'o'hog  islands 

o'l,    BRET     0     M 
^,'b»vS    O     U   N    D 

BRETON   I, 


MISSISSIPPI  RIVER 

FROM  THE  PASSES 
TO  GRAND  PRAIRIE. 


SCALE  OF  MILES 
I        I 
0 5       10 


Fig.  105. — The  Mississippi  delta. 


tributaries  (Figs.  104-106), 

which     spread     apart    and 

enter   the    sea  by  separate 

mouths.     The  delta  surface, 

though    very   level,    has    a 

gentle   grade    down   which 

the  river  water  can  flow. 
Deltas   are    absent    from 

many   coasts;  for   example, 

northeastern    America   and 

northwestern  Europe.    This 

is  because    there   has  been 

so    recent   sinking    of    the 

land  that  there  has  not  yet 

been  time  enough  to  build 

deltas.     It  is  where  the  sea 

bottom  is  remaining  at  one  level,  or  slowly  rising,  that  deltas 

are  most  common.  They  are 
more  easily  built  where  the 
water  is  shallow  than  where 
it  is  deep,  and  tlii^  is  one 
reason  why  they  are  so  com- 
mon in  lakes  (Figs.  107,  297). 
Absence  of  tides  and  large 
waves  is  another  reason  for 
so  many  deltas  in  lakes. 

Rivers  meander  on  deltas, 
as  on  floodplains.  Indeed, 
deltas  are  so  like  floodplains 
that,  as  they  grow  outward, 
their  upper  parts  are  com- 
monly called  floodplains 
They  make  excellent  farm 
land,  and  a  large  percentage 

of  the  human  race  is  now  living  on  deltas  and  floodplains. 


Fig.  106.  —  Tlie  Oriuoco  delta.  Notice 
its  triangular  form  between  the 
outer  distributaries. 


66  NEW  PHYSICAL   GEOGRAPHY, 

The  densest  population  of  China  and  India  is  centered  on 
the  deltas  and  floodplains  of  the  great  rivers,  and  a  large 
part  of  Holland  is  on  the  delta  of  the  Rhine.  The  low 
ground,  and  the  danger  of  floods  from  sea  and  river,  make 
living  in  such  situations  dangerous.  Millions  of  people  in 
India  and  China  have  been  drowned  during  floods;  but  the 
other  attractions  are  so  great  that  these  river-made  plains 
are  densel}^  settled. 

Summary.  — Deltas  are  level  x>lains,  built  up  by  the  deposit  of  sedi- 
ment at  river  mouths;  they  are  commonly  triangular  in  shape  be- 
cause crossed  by  branching  distributaries.  They  are  especially  well 
developed  in  lakes  and  other  places  ivhere  the  water  is  shallow,  the 
bottom  not  sinking,  and  waves  and  currents  not  strong.  Like  Jlood- 
plains,  they  form  excellent  farm  land,  and  are  densely  settled. 

44.  Alluvial  Fans.  —  A  stream  flowing  from  a  steep  to  a 
more  gentle  slope  has  its  velocity  checked.  If  it  has  much 
sediment,  some  may  be  deposited  where  the  slope  changes 
(Fig.  109).  Such  a  deposit  is  called  a  cone  delta.,  or  alluvial 
fan.  Some  are  small,  with  steep  slopes  (Fig.  108);  in  fact, 
they  may  be  seen  forming  at  the  base  of  clay  banks  after  a 
rain ;  and  some  are  very  large  and  fairly  level,  covering 
areas  of  thousands  of  square  miles.  They  resemble  deltas 
in  their  triangular  outlines,  and  some  of  the  larger  ones  are 
difficult  to  distinguish  from  deltas  (Fig.  110). 

As  in  a  delta,  the  water  flows  over  an  alluvial  fan  in 
numerous  shifting  distributaries  (Figs.  108,  110,  111).  As 
soon  as  one  channel  becomes  too  high,  it  is  abandoned  and 
a  lower  portion  of  the  fan  is  built  up.  Thus  the  fan  is  built 
up  regularl}^,  because  all  parts  of  it  are  reached  by  the  water. 

Mountainous  arid  lands  are  especially  favorable  to  the  formation 
of  alluvial  fans,  because  there  are  many  steep  slopes,  much  sedi- 
ment, and  usually  a  small  amount  of  water.  At  times  there  are 
heavy  floods,  bringing  much  sediment ;  but  at  other  periods  the 
water  disappears  by  evaporation  or  by  sinking  into  the  gravel. 


Fi(}.  108. — Two  alluvial  fans  being  Duiit  of  gravel  dropped  at  the  end  of 
sluices  in  the  process  of  washing  gold  from  the  gravels.  Notice  the  numer- 
ous branches  of  the  stream  on  the  farther  fan.  These  are  so  rapidly  deposit- 
ing and  building  up  the  fan  that  they  must  frequently  change  positions. 


Fig.  109.  — An  alluvial  fan  at  Chamonix  in  the  Alps,  built  at  the  mountain 
"las©  by  torrents  bringing  materials  from  the  steep  mountain  slopes. 


RIVERS  AND  RIVER    VALLEYS. 


67 


Allii^dal  fans  sometimes  grow  out  across  a  valley,  damming  the 
main  stream  and  forming  a  lake  (Fig.  113).  Tulare  Lake  in 
California  (Fig.  114),  for  example,  is  caused  by  the  low  alluvial 
fan  of  King  Eiver,  which  descends  from  the  Sierra  Nevada  to  the 
plain  of  the  valley 
of  California. 

Large  alluvial 
fans  are  excellent 
farming  land.  In 
arid  regions,  like 
western  United 
States,  they  are 
often  irrigated  be- 
cause (1)  the  soil  is 
good ;  (2)  there  is  a 
supply  of  water  at 
the  upper  part  of  the 
fan  ;  and  (3)  there  is 
a  good  grade  down 
which  to  lead  the 
water.  The  large, 
delta-like  alluvial 
fan  at  the  mouth 
of  the    Hoangho   of 

China  (Fig.  110)  is  the  seat  of  a  dense  agricultural  population. 
The  frequent  shiftings  of  the  river  over  this  fan  have  caused  enor- 
mous loss  of  life  by  drowning,  and  by  the  famines  that  have  resulted 
from  the  destruction  of  crops.  Even  in  a  single  flood  over  a  mil- 
lion people  have  been  killed.  The  Hoangho  has  even  been  used 
as  a  weapon  of  war,  being  turned  out  of  its  course  to  prevent  an 
invading  army  from  approaching. 

Summary.  —  Alluvial  fans  are  delta-like  deposits  made  ivhere 
streams  descend  from  steep  to  gentle  slopes,  as  at  the  base  of  moun- 
tains.    Large  alluvial  fans  are  important  agricultural  lands. 

45.  The  Filling  of  Valleys. — Many  valleys  are  having 
their  bottoms  raised  by  the  wash  of  sediment  from  their 
sides  (Figs.  Ill,  113).     This  is  especially  true  in  arid  regions 


Fig.  110.  —  Map  of  the  immense  alluvial  fan  of  the 
Hoangho.  Measure  with  scale  of  miles  the  dis- 
tance between  the  old  and  present  month. 


68 


NEW  PHYSICAL   GEOGRAPHY. 


•'m 


where  there  is  much  sediment  and  too  little  rain  to  carry  it 

off  to  the  sea. 

The  valley  of  California,  400  miles  long  and  50  to  80  miles 

wide,  furnishes  a  good  illustration  (Fig.   114).     From  the 

Coast  Ranges  and 
the  Sierra  Nevada 
the  raiil  wash  and 
the  streams  are 
dragging  sediment 
down  the  mountain 
slopes.  This  ac- 
tion builds  broad, 
flat,  alluvial  fans 
(Fig.  113)  near  the 
mountains,  and 
still  more  level  de- 
posits farther  out 
in  the  Valley. 


■'feiiMi 


5f:_C.    JSiJ:     -g^'i'i^:"'^-  "•■ 


Fig.  111. 


filling  a 
Ararat. 


The  distributaries  of  several  alluvial  fans, 
valley  among  the  mountains  near  Mt. 


A  similar  case  is  that  of  the  Po  valley  in  northern  Italy.  It 
was  once  an  arm  of  the  sea  between  the  Alps  and  the  Appennines, 
but  it  has  been  filled  by  wash  from  these  mountains,  and  is  still 
being  built  out  into  the  Adriatic.  The  many  mountain  streams 
are  forming  low  alluvial  fans  of  coarse  gravel  near  the  mountains  ; 
but  near  the  Po  the  sediment  is  finer  and  the  river  is  bordered  by 
fertile  farm  laud,  which  is  readily  irrigated  by  water  from  the 
mountain  streams  and  the  Po.  It  is  necessary  to  build  dikes  along 
many  of  the  streams  to  prevent  their  overflowing  the  plain.  Thus 
confined  to  their  channels,  the  rivers  are  obliged  to  deposit  sedi- 
ment in  their  beds.  In  consequence  of  this,  the  surface  of  the 
Po  is  now  well  above  the  level  of  the  surrounding  country. 

Summary.  —  The  wash  of  rode  fragments  from  inclosing  moun- 
tains sometimes  deeply  Jills  valleys,  especially  in  arid  lands. 


Fig.  112.  —  The  branching  course  of  the  Platte  Kiver  in  Nebraska,  which  has  so 
much  sediment  that  it  is  aggrading  its  bed,  and  doing  it  so  rapidly  that  it 
flows  not  in  a  channel,  but  in  a  braided  series  of  branches.  (Part  of  Kearney, 
Neb.,  Topographic  Sheet,  U.  S.  Geological  Survey.) 


Fig.  113.  — To  illustrate  valley  filling,  as  in  the  California  valley. 


f'lo.  114.  — Valley  of  California.  The  flat-bottomed  valley  is  deeply  filled 
with  sediment  washed  in  from  the  bordering  mountains.  Notice  Tulare 
Lake  formed  by  the  low  alluvial  fan  of  King  River.  (From  model  made  by 
N.  F.  Drake.) 


EIVERS  AND  RIVER    VALLEYS,  69 

Topical  Outline,  Questions,  ani>  Suggestions. 

Topical  Outline.  —  30.  Supply  ot  Water.  —  Underground  supply  ; 
run  off ;  variation  in  run  off ;  regulation  of  river  volume. 

31.  Rain  Sculpturing.  —  Conditions  favoring ;  results  ;  Bad  Lands. 

32.  The  Rock  Load  of  Rivers.  —  Dissolved  mineral;  rock  fragments; 
variation  in  size  ;  tools  of  c;rosion ;  great  load  carried. 

33.  Erosive  Work  of  Rivers.  —  Nature  of  work  ;  corrosion  ;  corrasion  ; 
lateral  cutting;  causes  for  variation  in  rate ;  influence  of  sediment;  de- 
grading ;  aggrading ;  influence  of  joint  planes ;  of  ice. 

34.  Waterfalls.  —  Relation  to  rock  ;  pot-hole  work  ;  water  power. 

35.  Young  Stream  Valleys.  —  (a)  Initial  drainage  on  a  plain  :  lakes ; 
divides;  tributaries ;  consequent  course,  (b)  Early  stages  of  develop- 
ment: steep-sided  valley;  waterfalls;  broadening  of  valley;  base  level; 
removal  of  lakes ;  narrowing  of  divides,  (c)  Meaning  of  youth  :  charac- 
teristics ;  illustration ;  age  in  years ;  comparison  with  plants. 

36.  The  Grade  of  a  Stream.  —  Nature  of  grade  ;  degrading  streams ; 
aggrading  streams. 

37.  Mature  Valleys.  —  Broadening  of  valleys ;  absence  of  lakes ;  of 
waterfalls ;  development  of  tributaries ;  of  divides ;  of  floodplains. 

38.  Old  Valleys.  —  Peneplains ;  reasons  for  general  absence. 

39.  Importance  of  Valley  Form.  —  Young  valleys ;  mature  valleys. 

40.  Springs  and  Underground  Channels.  —  (a)  Springs  :  causes  ;  situ- 
ation ;  mineral  springs,  {b)  Caverns:  cause;  underground  drainage; 
outlets;  stalactites;  stalagmites;  columns;  sinkholes;  natural  bridges. 

41.  River  Floodplains.  —  Where  found;  the  bluffs ;  cause  of  floodplains ; 
fitness  for  agriculture  ;  natural  levees  ;  levees ;  meanders ;  ox -bow  cut-offs. 

42.  River  Terraces.  —  Cause;  form;  frequency  in  soft  deposits ;  value. 

43.  Deltas.  —  Cause ;  name ;  origin  of  form ;  distributaries ;  sui'face 
slope;  favoring  and  opposing  conditions;  settlement;  dangers. 

44.  Alluvial  Fans.  —  Cause;  size;  form  ;  building  of  the  fan ;  location  ; 
formation  of  lakes ;  agriculture;  shifting  of  stream. 

45.  The  Filling  of  Valleys.  —  Favoring  conditions ;  valley  of  Califor- 
nia; valley  of  the  Po,  —  filling,  farm  land,  effect  of  dikes. 

Questions.  —  30.  In  what  ways  are  rivers  supplied  with  water? 
What  causes  variation  in  run  off?     What  serve  to  regulate  the  volume? 

31.  What  are  Bad  Lands?     Where  are  they  most  common?     Why? 

32.  In  what  two  forms  is  river  load  carried?  How  is  each  supplied? 
What  is  the  effect  of  differences  in  current?  What  effect  have  the  rock 
fragments  on  erosion  ?     Give  an  illustration  of  river  load. 

33.  By  what  two  means  are  rivers  wearing  at  their  channels?  What 
effect  have  they  on  their  banks  ?  State  the  several  causes  which  influ- 
ence the  rate  of  river  erosion.     Define  degrading  and  aggrading  rivers. 


70  NEW  PHYSICAL   GEOGRAPHY. 

84.  What  is  the  most  common  cause  for  waterfalls?  Give  an  illustra- 
tion.    What  causes  pot  holes?     Of  what  use  are  falls  and  rapids? 

35.  What  are  the  characteristics  of  new  diiiinage  on  a  plain  ?  What 
changes  occur  in  valley  form,  lakes,  tributaries,  and  divides?  What  is 
a  consequent  course?  Base  level?  State  the  characteristics  of  young 
valleys.     What  does  the  term  iJoulh  mean? 

36.  What  is  grade,  and  what  causes  it  to  vary? 

37.  What  changes  in  valley  form  occur  after  a  stream  has  reached 
grade?  What  about  lakes  and  falls?  What  changes  occur  in  tribu- 
taries?    What  influence  does  this  have  on  sediment? 

38.  What  is  a  peneplain?     Why  are  they  so  uncommon ? 

39.  What  influence  have  young  valleys  on  man?     Mature  valleys? 

40.  State  the  causes  for  springs.  What  causes  caverns?  What 
deposits  are  made  in  them  ?     What  are  sink  holes?     Natural  bridges? 

41.  What  causes  floodplains?  Why  are  they  level?  Of  what  im- 
portance are  floodplains?  What  is  the  natural  levee?  AVhat  causes 
meanders?     Ox-bow  cut-offs? 

42.  What  is  the  cause  of  terraces?     Of  what  value  are  they? 

43.  What  is  the  cause  of  deltas  ?  Why  so  named  ?  What  gives  the 
delta  form  ?  What  conditions  favor  and  what  oppose  their  formation  ? 
What  about  the  population  of  deltas  and  floodplains? 

44.  What  are  the  characteristics  and  causes  of  alluvial  fans?  Where 
do  they  occur?     Of  what  importance  are  they? 

45.  In  what  manner  is  the  valley  of  California  being  filled?  The  Po 
valley?     Of  what  importance  is  this  valley  filling? 

Suggestions. —  (1)  What  is  the  source  of  the  water  of  your  nearest 
stream?  Does  it  vary?  Why?  If  there  were  no  underground  supply 
would  it  in  any  way  affect  you  ?  ("2)  AVliere  does  the  water  run  off 
most  rapidly,  on  a  road,  a  grass-covered  lawn,  or  in  the  woods? 
Answer  from  your  own  observations.  Why  does  it  run  off  faster  in 
one  place  than  in  another?  From  which  place  is  most  sediment  washed 
to  the  streams?  (3)  Make  a  little  channel  in  the  ground  and  pour  water 
into  it,  varying  the  amount  from  a  small  flow  to  a  flood.  Now  make  a 
small  pond,  say,  five  feet  long,  with  the  little  channel  for  its  outlet.  Pour 
the  same  amount  of  water  into  the  pond  that  you  did  into  the  channel. 
Does  the  outflow  channel  show  the  same  variation  in  volume?  (4)  AVeigh 
a  stone  in  the  air  with  a  spring  balance.  Weigh  the  same  stone  sub- 
merged in  water  on  the  end  of  a  string.  What  does  the  result  show? 
(5)  INIake  a  little  trough  of  rough  wood  and  let  water  run  through  it  from 
a  faucet.  On  the  bottom  of  the  trough  place  small  pebbles,  sand,  and 
claj^  Vary  the  velocity  of  the  water  to  see  what  happens.  Record  your 
results.     (6)  Has  the  stream  nearest  you  a  rapid  or  slow  flow?     What 


RIVERS  AND  RIVER   VALLEYS.  71 

is  the  size  of  the  rock  fragments  that  it  carries  at  ordinary  times?  At 
times  of  flood?  Why  the  difference?  Is  the  material  at  the  bottom 
coarser  than  that  suspended  in  the  current?  Where  do  the  rock  frag- 
ments come  from?  (7)  Are  the  streams  near  your  home  aggrading  or 
degrading?  Jf  degrading,  are  tliey  aggrading  in  some  parts?  Why? 
What  differences  in  work  do  you  see  from  time  to  time?  Does  rock 
structure  influence  the  worlv  ?  Observe  the  stream  in  winter  and  spring 
to  see  if  ice  helps.  Do  you  know  of  any  places  where  they  are  cutting 
{>.e"ainst  the  banks?  (8)  Are  there  any  falls  or  rapids?  What  causes  them  V 
Are  there  any  pot  holes?  Find  what  is  in  the  bottom.  W'hat  does  this 
show?  (9)  Look  for  evidences  of  rain  sculpturing  on  roads,  in  plow  el 
fields,  or  under  gutters.  Place  some  flat  pebbles  on  some  clay  and  wash 
it  away  with  a  sprinkling  pot.  Are  any  columns  formed?  (10)  Has  the 
stream  nearest  you  reached  grade  ?  Is  the  valley  young  or  mature  ?  Study 
and  describe  the  valley,  —  its  form,  tributaries,  divides,  and  falls  and  lakes 
(if  present).  AVhat  influence  has  the  valley  on  roads,  railways,  and  in- 
dustries? (11)  Has  -your  river  a  floodplain  ?  Is  the  plain  ever  flooded? 
If  so,  go  after  the  next  flood  to  see  if  deposits  of  sediment  have  been  made. 
Does  the  river  meander?  Have  there  been  any  changes  in  the  meanders? 
(12)  Terraces  are  common  in  sections  where  streams  are  cutting  away  gla- 
cial deposits.  Are  there  any  near  your  home?  If  so, study  and  describe 
them.  (18)  If  there  is  a  pond  or  lake  near  by,  see  if  there  are  not  del- 
tas opposite  the  mouths  of  both  the  large  and  small  streasns.  If  so, 
report  on  what  you  observe  concerning  their  form  and  the  material  of 
which  they  are  m;ide.  (14)  Are  there  any  alluvial  fans?  Look  for 
them  in  mud  puddles  at  the  base  of  a  clay  cliff,  for  example  in  a  railway 
cut.  You  can  make  one  by  building  a  pile  of  clay  with  steep  slope  and 
washing  the  clay  do"wn  to  the  base  with  a  sprinkling  pot. 

Reference  Books.  —  Russell,  Rivera  «f  North  America,  Putnam's 
Sons,  New  York,  1898,  r2.00 ;  T ark,  Physical  Geography  of  New  York 
State,  Chapter  V,  :\Tacmillan  Co.,  New  York,  1902,  $3.50;  Hovey,  Cele- 
hrated  American  Carerns,  Robert  Clarke  Co.,  Cincinnati,  1896,  $2.00; 
Shaler,  Aspects  of  the  Earth,  Chapters  HI  and  IV,  Scribner's  Sons,  New 
York,  1900,  $2.50;  Huxley,  Physiography,  jNIacmillau  Co.,  New  York, 
1891,  $1.80.     See  also  Chapter  XVI  of  this  book. 


CHAPTER   V. 

PLAINS,   PLATEAUS,   AND   DESERTS 

PLAINS. 

46.  Continental  Shelf  Plains.  —  Off  the  coast  of  eastern 
North  America  there  is  a  sea-bottom  plain  sloping  out  into 
deep  water  (Fig.  116).  It  attains  a  width  of  50  or  100  miles, 
and  its  outer  edge  is  covered  by  about  600  feet  of  water.  The 
surface  is  a  level  expanse  of  sand  near  the  coast,  and  of  mud 
farther  out.  The  plain  is  made  of  layer  upon  layer  of  sedi- 
ment washed  from  the  land,  and  the  waves  and  currents  are 
constantly  adding  to  it.  Other  continents  are  bordered  by 
similar  sea-bottom  plains,  or  continental  shelves  (Fig.  316). 

Should  this  sea  bottom  be  raised  600  feet,  a  broad  strip  of 
plain  would  be  added  to  the  American  continent.  It  would 
slope  at  the  rate  of  a  few  feet  a  mile,  and  the  rain  that  fell 
upon  it  would  find  such  difficulty  in  passing  off  that  much  of 
the  surface  would  be  swampy. 

Summary.  —  Continents  are  bordered  by  sea-bottom  plains,  or 
continental  shelves,  made  of  sediment  from  the  land, 

47.  Coastal  Plains.  —  Uplifts  have  actually  added  such 
plains  to  the  land  (Figs.  122,  123).  Some  are  narrow  strips 
at  the  base  of  mountains,  as  in  western  South  America  (Fig. 
117),  where  the  land  is  still  rising ;  others  are  many  miles 
wide,  like  the  plain  that  skirts  the  coast  south  of  New  York. 
Because  they  border  the  coast  they  are  called  coastal  plains. 

Tlie  coastal  plain  of  the  Atlantic  and  Gulf  coasts  extends 
from  New  Jersey  to  the  Rio  Grande,  and  includes  the  penin- 
sula of  Florida.  Wells  bored  into  it  pass  through  hundreds 
of  feet  of  gravel,  sand,  and  clay,  often  finding  water  in  the 

72 


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Fig.  117.  —  Narrow  coastal  plaiu  of  Western  South  America,  a  few  miles  wide. 


Fig.  118.  —  Diascram  to  illustrate  the  cause  for  artesian  wells  on  a  coastal  p.uiii. 
Water  passes  down  the  porous  layer  P,  and  is  prevented  from  rising;  or  going 
deeper  by  the  impervious  layers,  /,  I.  When  a  well  is  bored  down  to  tht 
porous  layer  the  water  rises  to  the  surface  because  it  has  entered  higher  than 
the  outlet  of  the  well,  and  is  under  pressure  of  the  water  in  the  porous  layer, 
which,  therefore,  forces  it  out.  Such  a  well  may  even  be  bored  on  a  sand  bar 
in  the  sea,  finding  water  beneath  the  impervious  layer. 


Fig.  119. — The  Florida  plain  along  the  St.  John  River. 


Fig.  120.  —  A  view  of  the  palraettoes  on  the  Florida  plain. 


PL  Am  8,  PL  ATE  AXIS,  AND  DESERTS. 


73 


Fig.   122.  —  A  sea-bottom  plain  being  formed  by  the 
deposit  of  sediment  on  a  submerged  old  laud. 


porous,  sandy  layers.  Where  the  water  rises  to  the  surface,  it 
is  called  s.n  artesian 
well  (Fig.  118). 
There  are  hun- 
dreds of  such  wells 
along  the  Atlantic 
coast  (Fig.  115), 
and  many  cities, 
such  as  Galveston, 
obtain  drinking 
water  from  them. 
Artesian  water  is 
pure  and  free  from 
the  germs  that 
abound  in  surface 
drainage. 

Much  of  the 
coastal  plain  is  so 
sandy  that  it  is 
poorly  adapted  to 
agriculture,  and  is 
still  occupied  by 
an  open  pine  forest 
in  which  cattle 
roam,  feeding  on 
the  scattered  grass. 
The  forest  supplies 
valuable  lumber, 
turpentine,  tar,  and 
other  products. 
The  higher  and 
less  sandy  tracts 
are  favorable  to 
agriculture,  pro- 
ducing fruit,  grain,  etc.,  in  Maryland,  Delaware,  and  other 


Fig.  123.  —  Same  as  Fig.  122,  elevated  to  form  a  coastal 
plain.  Rivers  from  the  old  land  are  extended  out 
upon  the  coastal  plain.  This  is  the  condition  of 
the  coastal  plain  southward  from  New  York. 


74 


NEW  PHYSICAL   GEOGRAPHY. 


states,  and    cotton,  corn,  and  other   products  in  tlie  South. 

Along  the  coast   and    near  the  rivers  the  land  is  swampy, 

being  useful  in  the  South  for  rice  culture. 

A  slight  sinking  of  this  coastal 
plain  has  admitted  the  sea  into 
the  valleys,  transforming  their 
mouths  to  shallow  bays  (Figs. 
121,  124),  the  seats  of  oyster  and 
fishing  industries.  Some  of  the 
deeper  bays  have  good  harbors, 
thouoh  a  frinore  of  sand  bars 
partly  cuts  off  the  entrance  to 
many.  The  shallower  bays  and 
tide-water  rivers  are  navigable 
b}'  small  craft,  thus  opening  up 
large  areas  of  country  to  water 
transportation.  This  has  helped 
greatly  in  carrying  cotton  and 
other  products  to  the  seaports  for 
shipment.  Chesapeake  Bay,  with 
its  many  branches,  is  the  largest 
of  the  coastal  plain  ba3"s. 

For  the  most  part  the  rivers  of 
the  coastal  plain  are  sluggish,  and, 
in  some  places,  the  slope  of  the 
plain  is  so  gentle  that  water  does 
not  run  off.  This  causes  swamps,  as  in  parts  of  Florida  (Figs. 
78,  79,  119),  and  the  Dismal  Swamp  (Fig.  307).  In  Texas, 
south  of  Houston,  the  divides  are  so  flat  and  swampy  tliat  there 
is  no  agriculture,  and  not  even  cattle  can  find  support.  Tlie  sur- 
face of  the  Florida  plain  is  so  young,  and  the  streams  have  so 
little  sediment,  that  the  shallow  lakes  in  depressions  of  the  old 
sea  bottom  have  not  yet  been  filled.  Where  the  streams  have 
cut  into  this  coastal  plain  tliey  occupy  shallow,  steep-sided  val- 
leys, with  broad,  flat-topped  divides  (Fig.  121),  along  whose  le\el 
surface  the  roads  run. 


BORMAY  i  Cu,  N.V. 


Fig.  124.  —  The  branching  Chesa- 
peake. The  lines  sliow  the 
probable  position  of  the  riv- 
ers that  formed  this  branch- 
ing, submerged  valley. 


PL  A 11^  S,   PLATEAUS,   AND   DESERTS, 


75 


Where  streams  pass  from  the  older  land  to  the  coastal 
plain  (Fig.  123),  tlieir  slopes  increase  and  their  courses  are 
interrupted  by  rapids  and  falls.  The  explanation  of  this  fact 
is  that  the  rivers  have  cut  faster  in  the  soft  clays  and  sands  of 
the  plain  than  in  the  harder  rocks  of  the  old  land.  Fcr  this 
reason  the  boundary  between  the  old  land  and  the  plain  is 
called  the  Fall  Line  (Fig.  125).  It  has  had  a  very  important 
influence  on  settlement.  Even  in 
the  days  of  the  Indians,  village 
sites  on  the  rivers  were  located 
along  this  line,  —  the  highest 
points  to  which  canoes  could  go 
from  the  seaward  side,  and  where 
portages  were  necessary  to  pass 
higher  upstream.  White  men  have 
located  cities  on  these  same  spots, 
the  farthest  points  to  which  boats 
from  the  sea  can  pass  inLand. 
Along  the  Fall  Line  are  located 
Trenton,  Philadelphia,  Baltimore, 
Washington,  Richmond,  Raleigh, 
Columbia,  and  Augusta. 

Summary. —  Upraised  sea  bottoms 
form  coastal  plains  slcirting  the  coasts  of  continerits.  There  is  a 
ivell-clejiiied  one  from  New  Jersey  to  Mexico,  much  of  ichose  level  sur- 
face is  too  sandy  or  swampy  for  agriculture,  while  in  Florida  there 
are  many  lakes  still  occupying  the  original  depressions.  A  slight 
sinking  has  admitted  the  sea  into  the  river  mouths,  transforming 
them  to  shallow  bays.  Where  streams  descend  from  the  old  land  to 
the  plain  there  is  a  line  of  rapids  and  falls,  called  the  Fall  Line. 

48.  The  Russian  and  Siberian  Plains.  —  This,  the  greatest 
expanse  of  plains  on  any  continent  (Fig.  21),  covers  an  area 
far  greater  than  the  entire  United  States.  These  plains 
extend  from  the  Caspian  region  to  the  Arctic,  including  a 
large  part  of  northern  Asia  and  much  of  Russia,  with  a 


Fig.  125.— The  Fall  Line.  Coastal 
plain  dotted  ;  cities  printed 
in  hea\'y  type  are  located 
along  the  Fall  Line. 


76  NEW  PHYSICAL   GEOGRAPHY, 

western  branch  reaching  to  Holland.  They  are  made  of 
layers  of  sand,  gravel,  and  clay,  washed  from  the  mountains 
of  Asia  and  Europe  into  a  sea  which  has  been  destroyed  by 
uplift.  The  uplift  of  this  sea-bottom  plain  has  been  so  re- 
cent that  the  streams  are  young ;  there  are  many  swamps  ; 
shallow  lakes  are  yet  unfilled  ;  and  the  divides  are  flat-topped. 

In  the  North  there  is  barren  tundra,  inhabited  by  scattered 
tribes  (Fig.  126)  who  use  the  reindeer  as  a  domestic  animal  (Fig. 
546).  The  soil,  frozen  to  great  depth,  thaws  in  summer  only  at  the 
surface,  making  the  land  a  vast  swamp ;  in  winter  the  tundra  is  a 
bleak,  frozen,  snow-covered  desert.  Toward  the  south  it  grades 
into  the  forest  region  which  is  now  being  cleared  and  opened  to 
agriculture  as  a  result  of  the  building  a^  the  Siberian  railway.  This 
forest  section  is  destined  to  become  one  of  the  great  farming 
regions  of  the  world.  On  its  southern  side  the  forest  belt  grades 
into  the  open,  grass-covered  steppes  (p.  285),  a  region  too  arid  for 
farming,  and,  therefore,  occupied  by  a  nomadic,  pastoral  people. 

Summary: —  Vast  plains,  caused  hy  recent  uplift  &f  an  ancient  sea 
bottom,  occupy  a  large  part  of  northern  Asia  and  Europe.  There  is 
harr en,  frozen  tundra  in  the  north,  barren,  arid  steppe  land  in  the 
south,  and  forest  and  farm  land  between. 

49.    Plains   and   Prairies   of    Central    United   States.  —  In 

ancient  geological  times  a  sea  bottom  between  the  moun- 
tains of  eastern  and  western  North  America  was  also  raised 
above  sea  level.  From  time  to  time  it  has  been  reelevated, 
and  numerous  additions  have  been  made  to  its  southern  mar- 
gin. Denudation  has  also  been  at  work,  lowering  and  sculp- 
turing its  surface,  so  that  in  places  it  is  hilly.  It  forms  one 
of  the  largest  areas  of  plains  in  the  world  (Fig.  21). 

Near  the  Appalachian  Mountains  the  plains  reach  an  ele- 
vation of  2000  to  3000  feet  ;  near  the  Rocky  Mountains  they 
rise  from  5000  to  6000  feet  above  sea  level.  From  these 
higher  portions,  really  plateaus,  the  surface  slopes  toward  the 
Mississippi,  making  a  broad  valley  which  that  river  follows, 
receiving  long  tributaries  down  the  slopes  from  either  side. 


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v.-^.  128.  —Cattle  on  the  Great  Plains. 


t~ 


\f 


"W"  -^  ^f^'  ■««■'*• '.-  "  .«l»i».J^ 


Fig.  129.  —  The  great  plains  in  Montana,  near  the  base  of  the  Crazy  JMountainfi 


PLAINS,   PLATEAUS,  AND  DESERTS.  77 

The  plains  west  of  the  Mississippi  are  called  the  Great 
Plains  (Figs.  127-129).  In  the  eastern  part  tliey  have  rain- 
fall enough  for  agriculture  ;  but  west  of  the  100th  meridian 
they  are  suited  only  to  grazing,  though  here  and  there  rivers 
and  artesian  wells  supply  water  for  irrigation.  Where  the 
rainfall  is  light  there  is  timber  only  along  the  streams.  In 
early  days,  when  Indians  occupied  them,  crossing  these  vast 
plains  was  a  difficult  and  dangerous  undertaking. 

East  of  the  Mississippi  are  large  areas  of  plain,  called 
prairies,  which,  when  discovered,  were  also  free  from  forest. 
In  some  cases  the  treeless  condition  was  due  to  fires,  set  by 
Indians  in  their  buffalo  hunts.  In  others  the  fine-grained 
soil  seems  to  have  been  unfavorable  to  tree  growth,  but  favor- 
able to  a  luxuriant  growth  of  prairie  grass.  These  fertile, 
treeless  prairies  helped  greatly  in  the  settlement  of  the 
Middle  West.  A  crop  could  be  raised  the  first  year,  for 
there  was  no  laborious  work  of  clearing  land  for  farming  ; 
and,  when  this  was  found  out,  settlers  came  rapidly  and 
prospered. 

Plains  are  not  usually  great  mineral-producing  regions,  but 
are  especially  suited  to  agriculture  when  the  climate  is  moist, 
and  to  grazing  when  arid.  Yet,  in  the  plains  of  central 
United  States,  beds  of  sandstone  and  limestone  furnish 
abundant  building  stone  ;  layers  of  salt  are  found  ;  deposits 
of  iron,  lead,  and  zinc  occur  ;  and  there  are  vast  quantities 
of  natural  gas,  petroleum,  and  coal.  Where  coal  is  present, 
busy  manufacturing  cities  spring  up,  especially  if  agriculture 
flourishes,  supplying  materials  for  manufacture  and  a  market 
for  manufactured  products.  These  conditions  all  exist  on 
the  plains  of  central  United  States. 

Each  of  the  continents  has  plains  similar  to  those  already 
described.  The  great  plains  of  the  Amazon,  of  Argentina, 
and  of  Venezuela  are  instances.  A  very  large  part  of  the 
land  surface  consists  of  plains  (Fig.  21)  that  at  one  period 
or  another  have  been  raised  from  the  sea. 


78 


NEW  PHYSICAL   GEOGRAPHY. 


Summary.  —  TJie  ancient  and  much  worn  plains  of  central  United 
States  slope  from  the  mountains  on  each  side,  forming  the  great 
Mississipjyi  valley.  In  the  West  the  Great  Plains  are  treeless,  because 
arid  ;  in  the  East,  though  the  climate  is  moist,  large  areas,  called 
prairies,  were  treeless  because  of  the  effect  of  fires  ayid  the  compact 
soil.  These  plains,  adapted  to  agriculture  where  humid,  and  grazing 
where  arid,  also  contain  mineral  wealth,  and,  in  the  humid  portion, 
have  become  a  prosperous  and  busy  manufacturing  region. 

50.  Lake  Plains.  —  Sediment  deposited  in  a  lake  levels  its 
bottom.     If  the  Caspian  Sea  or  Lake  Erie  could  be  drained,  their 

sites  would  become 
'^^m^mMmWs  -'\  I      broad  plains.    There 

are  places  from 
which  lakes  havedis- 
appeared.  Extinct 
lakes  of  this  sort 
were  formed  by  a 
great  ice  dam  across 
north-flowing 
streams  when  the 
glacier  was  melting 
from  North  America 
(p.  149). 

An  enormous  lake 
of  this  kind,  glacial 
Lake  Agassiz  (Fig. 
130),  larger  than  all  the  Great  Lakes  combined,  existed  in  the  val- 
ley of  the  Red  River  of  the  North.  The  fine-grained  sediment 
that  was  deposited  on  the  bottom  of  this  extinct  lake  has  made  a 
fertile  plain  (Figs.  131, 132),  one  of  the  most  famous  wheat  regions 
of  the  world.  Its  surface  is  so  smooth  that,  after  a  rain,  water 
stands  on  the  ground  in  sheets. 

A  large  lake  also  once  existed  in  the  Great  Basin,  round  Great 
Salt  Lake.  When  the  climate  became  arid  this  lake  was  dimin- 
ished by  evaporation,  leaving  only  small  remnants,  of  which 
Great  Salt  Lake  is  the  largest.  These  remnants  occupy  shallow 
depressions  in  the  level  lake-bottom  plain  (Figs.  133,  150,  301). 


Fig  130.  —  Extent  of  the  extinct  glacial  Lake  Agas- 
siz, -wbieh  occupied  Uie  valley  of  the  Red  River 
of  the  NortL. 


Y 


SCALE   OF    MILES 


CONTOUR  INTERVAL  20  fEET 


BOilM^   4    &I).|  N.t. 


KO 


Fig.  131. — The  lake-bottom  plain  of  the  valley  of  the  Red  River  ot  iiie  North. 
Notice  how  very  level  it  is  (see  also  Fig.  132).  (Fargo  Sheet,  U.  S.  GeologieaJ 
Survey   *• 


Fig.  132.  — Wheat  fields  on  the  Red  River  valley  plains  (Fig.  131).    These 

plains  are  almost  as  level  as  the  sea. 


Fi©.  133. —  Salt  Lake  City,  on  the  plain  formed  in  the  hottom  of  ancient  Lake 

Bonneville  (Fig.  301). 


PLAINS,   PLATEAUS,   AND  DESERTS.  79 

There  are  a  number  ,of  other  classes  of  plains.  Some  of  these 
are  described  in  the  chapters  on  Glaciers  (p.  149)  and  Lakes 
(p.  165) .  Others,  formed  by  rivers,  have  already  been  described,  — 
tlood plains  (p.  61),  delta  plains  (p.  64),  alluvial  fan  plains  (p.  66), 
and  filled  valley  plains  (p.  67). 

Summary.  —  On  lake  bottoms  sediment  makes  plains  which  may 
become  dry  land  by  the  disappearance  of  the  lakes,  as  in  the  valley 
of  the  Red  River  of  the  North,  and  the  Greed  Basin. 

51.  Life  History  of  a  Plain.  — A  young  plain  (p.  54)  has  a 
level  surface,  poorly  defined  and  perhaps  swampy  divides,  and 


Fig.   134.  —  To  illustrate  the  life  history  of  a  plain  in  uniform  rock  {A),  through 
youth  {B),  to  maturity  (C),  and  old  age  {D). 

shallow  lakes.  The  consequent  streams  at  first  cut  steep- 
sided  valleys,  with  falls  where  differences  in  rock  hardness 
are  found. 

In  time  the  lakes  are  filled,  grade  is  established,  falls 
disappear,  tributaries  increase  in  number,  divides  narrow  up, 
and  the  valleys  broaden  (p.  57).  Such  a  mature  plaiii  has  an 
undulating  surface,  and,  if  high,  it  may  be  so  dissected  as  to 
become  a  hilly  laud  (tig.  134).  In  an  old  plain  the  valleys 
are  so  broadened  that  the  surface  again  becomes  nearly  level. 

The  rock  layers  of  a  plain  usually  lie  in  sheets,  gently  inclined  in 
the  direction  given  them  by  uplift  of  the  land  (Fig.  118).  As  the 
surface  of  the  plain  is  slowly  worn  down,  durable  layers,  since 
they  resist  deimdation  better  than  weak  ones,  are  left  as  uplands, 
possibly  only  a  few  feet,  perhaps  scores  of  feet,  above  the  lower 
portions  of  the  plain.  Being  in  sheets,  the  durable  layers  form 
belts  of  hilly  land  bounded  on  either  side  by  belts  of  lower  land, 
where  the  weaker  strata  lie  (Fig.  135).  The  plain  is,  therefore, 
sculptured  into  bands,  or  belts,  of  different  level,  corresponding 


80 


NEW  PHYSICAL   GEOGRAPHY. 


to  the  differences  in  the  strata.     Such  a  land  surface,  found  both 
on  recent  coastal  plains,  as  in  eastern  United  States,  and  on  older 

plains,  as  in  central 
United  States,  is 
known  as  a  belted 
plain. 

Summary.  —  A 
young  plain  has  a  level 
surface  aiid  a  young 
drainage  system ;  a 
mature p)la in  has  b  road 
valleys  and  a  hilly 
surface;  an  old  plain 
has  a  level  surface 
again.  Abelted  struc- 
ture often  7^esults  from 
the  less  ixipiid  removal 
of  the  more  resistant 
strata. 


Fig.  135. — A  belted  coastal  plain.  The  different 
symbols  (dots  and  lines)  represent  different  lay- 
ers of  rock,  gently  inclined  toward  us. 

PLATEAUS. 


52.  Nature  of  Plateaus.  —  When  mountains  are  nj^lifted 
the  country  on  either  sic^e  is  also  raised,  often  without  much 
folding  of  the  strata.  As  the  mountains  rise  higher  the 
adjoining  plains  become  more  elevated,  especially  near  the 
mountains  and  between  the  ranges.  They  may  rise  so  high 
that  they  deserve  the  name  plateaus,  for  a  plateau  is  only  an 
elevated  plain.  The  plateau  along  the  western  base  of  the 
Appalachians  (Fig.  146)  is  2000  to  3000  feet  above  sea  level; 
at  the  eastern  base  of  the*Rocky  Mts.  (Fig.  129),  from  5000 
to  6000  feet;  between  the  Rockies  and  the  Sierra  Nevada, 
often  7000  to  8000  feet;  north  of  the  Himalayas  (Fig.  136), 
over  10,000  feet. 

Owing  to  the  close  relation  between  plateaus  and  moun- 
tains (Fig.  136),  the  strata  of  plateaus,  though  mostly  hori- 
zontal, are  sometimes  broken  and  tilted;  in  fact,  there  is  every 


Fig.   137.  —  Map  of  a  young  river  system  on   the  plateau  of    northern  New 
Mexico.     (Part  of  Watrous  Sheet,  U.  S.  Geological  Survey.) 


S200      *, 


LONE   CONE  DOLORES    MTS.        SAN    MIGUEL   MTJ, 


LA.  piArA  ura. 


Fia.  138.  —  Canyon  of  the  Dolores  River,  New  Mexico  "  vouug  stream  valley  ou 

an  arid  plateau. 


PLAINS,   PLATEAUS,   AND  DESERTS.  81 

gradation  from  slightly  tilted  plateau  blocks  (Fig.  155)  to 
true  mountains.  Lava  has  often  welled  from  the  fissures, 
flooding  large  areas  of  country,  as  in  the  Columbia  and  Snake 
River  valleys  (Fig.  476). 

Summary.  —  Plateaus  are  elevated  plains,  raised  during  mountain 
uplift,  with  strata  usually  horizontal,  though  sometimes  tilted. 

53.  Sculpturing  of  Plateaus.  —  Rivers  upon  plateaus  have 
much  the  same  history  as  upon  plains  (p.  54);  and  the  life 
history  of  a  plateau  is  much  the  same  as  that  of  a  plain 
(p.  79).  But,  being  higher  above  base  level,  the  streams 
have  more  work  to  perform,  and  this  takes  a  longer  time. 
Young  streams  sculpture  plateaus  into  extremely  rugged 
form,  with  flat-topped  divides,  and  deep,  steep-sided  valleys, 
with  falls  and  rapids.  The  valleys  grow  broader,  the  sur- 
face lower,  and  finally,  in  old  age,  the  land  is  level  again. 

The  sculpturing  of  plateaus  is  frequently  retarded  by  the 
fact  that  the  climate  is  arid  and  denudation  therefore  slow 
(p.  41).  For  this  reason  many  arid  land  plateaus  are  still  in 
the  rugged  stage  of  youth,  even  though  in  years  they  may  be 
far  older  than  maturely  dissected  plateaus  of  humid  regions. 
For  the  same  reason  arid  plateaus  have  an  angular  topogra- 
phy (Figs.  140,  148),  while  in  moist  climates  denudation 
more  commonly  rounds  the  edges  of  the  strata. 

Summary.  —  Plateaus,  like  plains,  pass  through  stages  of  youth, 

maturity,  and  old  age.     But,  since  they  are  higher,  the  time  required 

to  lower  them  is  longer,  and  the  land  forms  produced  are  more  rugged. 

The  arid  climate  of  many  p)lo.teaus  retards  denudation  and  therefore 

prolongs  youth. 

54.  Canyons.  —  A  canyon  is  the  deep,  steep-sided  valley  of 
a  young  plateau  stream  (Figs.  137, 138).  Canyons  are  found 
on  most  plateaus,  being  a  characteristic  result  of  the  early 
stages  of  river  erosion  in  high  plateaus.  By  far  the  best  in- 
stance is  the  Grand  Canyon  of  the  Colorado.  (Frontispiece ,- 
see  also  p.  322.) 

o 


82 


NEW  PHYSICAL  GEOGUAPBT, 


For  about  200  miles  the  Colorado  River  flows  in  a  canyon, 
in  one  place  6000  feet  in  depth  —  the  deepest  canyon  in  the 
world.  Some,  of  the  grandest  scenes  in  nature  are  the  views 
looking  down  into  this  river-made  valley  from  the  canyon 

edge,  or  looking  upward 
from  its  bottom.  The  inter- 
nal structure  of  the  earth's 
crust  is  here  revealed  — 
thousands  of  feet  of  strata, 
layer  on  layer,  appearing 
one  beneath  the  other.  One 
cannot  look  into  this  enor- 
mous  cut  in  the  earth  with- 
out realizing  the  vast  work 
which  a  river  can  do  when 
time  enough  is  allowed. 
Yet  it  is  the  work  of  a 
young  stream  still  cutting 
down  toward  grade. 


Summary.  —  Deep,  steep- 
sided  valleys  of  young  plateau 
streams  are  called  canyons.  The 
greatest  of  these  is  the  Can- 
yon of  the  Colorado,  over  200 
miles  long  and,  in  one  place, 
(jOOO  feet  deep. 


Fig.  139. —  The  Colorado  Canyon  from 
the  bottom.  A  view  showing  the 
wreck  of  one  of  Powell's  boats  in  his 
venturesome  trip  through  the  canyon. 


55.  Mesas  and  Buttes.  — In  plateaus  there  are  many  flat, 
table-like  surfaces  (Fig.  140)  faced  by  steep  slopes,  often  cliffs. 
These  are  mesas^  a  Spanish  word  meaning  table.  An  examina- 
tion of  such  a  mesa  shows  that  the  rock  on  the  top  is  hard, 
often  lava.  These  table-top  surfaces  are  due  to  the  fact  that 
the  more  durable  rock  layers  have  resisted  denudation  ;  and, 
since  they  are  nearly  horizontal,  have  held  the  surface  up  to 
a  general  level,  parallel  to  the  stratification. 


Fig.  140. —Mesa  Verde,  Colorado.  The  horizontal  hard  stratum  that  protects 
these  mesas  from  being  worn  away  has  a  steep  slope,  while  the  softer  strata 
beneath  have  a  more  gentle  slope. 


MSS^SB^K 


^mmmmmmm 


4 


Fig.  141.  —  Crow  Heart  Butte,  Wind  River,  Wyoming. 


Fig.  142.  —  A  superimposed  river,  reaching  folded  rock  beneath  the  horizontal 

strata  of  a  plateau. 


FiG.  143.  —  A  rejuvenated  river.  In  the  left-hand  fifjure  the  stream  has  reached 
grade  and  is  swinging  over  a  floodplain  in  a  gently  sloping,  mature  valley. 
In  the  right-hand  figure  the  land  has  been  uplifted  and  a  young  valley  is  sunk 
in  the  bottom  of  the  mature  valley,  preserving  some  of  the  meanders  that  the 
stream  had  before  the  uplift.    These  may  be  called  entrenched  meanders. 


PLAINS,   PLATEAUS,   AND  DESERTS. 


8S 


Small  detached  sections  of  mesas,  cut  off  by  denudation, 
are  called  buttes  (Figs.  141,  144).  They,  too,  are  capped  by 
durable  layers  which  have  preserved  thera  from  being  worn 
down.  The  pres- 
ence of  these  flat- 
topped  butte  and 
mesa  areas  ac- 
counts for  the  name 
tableland,  often 
given  phiteaus. 


Summary.  —  Flat- 
topped  areas,  called 
mesas  if  large,  hutle>i 
if  small,  due  to  t'le 
resistance  of  horizon- 
tal beds  of  hard  rock, 
are  common  amony 
"plateaus,  giving  rise 
to  the  name  tableland. 


Fig.  144.  —  A  butte  on  the  Great  Plains. 


56.  Superimposed  and  Rejuvenated  Rivers.  —  In  cutting  into  the 
strata  of  plains  and  plateaus,  rivers  may  wear  down  through  the 
horizontal  layers  to  buried  mountains  (Fig.  123).  Such  rivers  are 
uaid  to  be  sujyerimposed  on  the  buried  structure  (Fig.  142).  The 
Colorado  River,  for  example,  has  discovered  an  old,  buried  moun- 
tain mass  in  one  part  of  its  canyon. 

An  uplift  of  the  land  gives  a  river  new  life,  or  rejuvenates  it. 
The  stream  then  cuts  a  narrow  gorge  in  the  bottom  of  its  old 
valley  (Fig.  143).  Such  a  valley  is  rejuvenated,  or  made  young 
again. 

Summary.  —  Superimposed  rivers  are  those  tchich  cut  through  one 
set  of  layers  to  another  of  different  position.     A  r^uvenated  river  is 
me  made  young  again  by  any  cause,  as  by  uplift. 

57.  Climate  of  Plateaus.  —  High  plateaus  are  cold  because 
they  reach  into  cool  upper  layers  of  the  atmosphere.     On  tiiv 


84  NEW  PHYSICAL   GEOGRAPHY, 

plateau  of  Mexico,  for  instance,  the  climate  is  tropical  at 
the  base  ;  coffee  is  grown  on  the  lower  slopes;  but  grains  are 
the  chief  crops  on  top.  In  the  lower  Colorado  valley,  in 
Arizona,  the  summer  climate  is  almost  unbearably  hot,  wliile 
on  the  plateau  it  is  pleasantly  cool.  The  plateau  of  Tibet  is  so 
high  that  it  has  a  cold,  disagreeable  climate,  even  in  summer. 
Plateaus  are  often  associated  with  mountains,  which  shut 
out  the  rain-bearing  winds.  Many  plateaus  are  therefore 
arid,  and  some,  like  central  Asia  and  parts  of  western  United 
States,  are  true  deserts. 

Summary.  —  Platemis  have  a  cooler  climate  than  neighboring 
lowlands  ;  they  are  often  arid. 

58.  Inhabitants  of  Moist  Plateaus.  —  The  plateau  at  the 
western  base  of  the  Appalachians  (p.  80)  includes  the  Cats- 
kill,  Alleghany,  and  Cumberland  mountains.  It  is  dissected 
by  valleys,  often  1000  feet  deep  (Fig.  145),  with  sides  too 
steep  for  cultivation,  but,  owing  to  the  moist  climate,  clothed 
with  forest  (Fig.  146).  There  are  no  true  buttes  and  mesas, 
and  no  real  canyons ;  but  the  surface  is,  nevertheless,  very 
rugged. 

Much  of  this  plateau  is  a  wild  region,  with  a  sparse  popu- 
lation, and  with  its  forest  areas  still  occupied  by  wild  animals. 
It  is  an  important  source  of  timber.  The  scattered  farms 
are  poor  and,  south  of  Pennsylvania,  where  the  rugged, 
timber-covered  surface  interferes  with  communication  with 
the  outer  world,  there  are  sections  in  which  the  people  are 
very  backward.  Many  cannot  read  or  write;  illicit  distilling 
of  whisky  is  one  of  the  industries;  and,  in  some  parts,  there 
are  family  feuds  and  lawlessness,  resulting  in  much  loss  of  life. 

The  discoverv  of  coal  has  led  to  the  opening  of  parts  of 
this  plateau  tcr  other  occupations  than  lumbering  and  the 
crude  farming  of  the  backwoodsmen.  In  this  respect  the 
plateau  of  western  Pennsylvania  has  advanced  far  beyond 
that  of  West  Virginia,  Tennessee,  and  Kentucky.     In  New 


Fig.  145.  —  The  hilly  plateau  of  southwestern  New  York.     (Part  of  Salamanca 

Sheet,  U.  S.  Geological  Survey.) 


HI 

a. 
o 


o 

<XI 


-t-» 

'a 

03 
<» 


H 


PLAINS,  PLATEAUS,  AND  DESEHTB,  86 

York  (Fig.  145)  the  plateau  is  less  rugged,  and,  consequently, 
better  developed.  It  lias,  in  large  part,  been  cleared  of  for- 
est, and  farm  lands  have  been  developed  wherever  possible. 
Yet  even  here  the  upland  farms  are  poor  in  quality. 

Summary.  —  Rugged,  dissected  plateaus  in  moist  countries,  like 
:hat  ivest  of  the  Appalachians,  are  largely  forest-covered,  poorly 
.tdapted  to  farming,  and,  unless  influenced  by  the  development  of 
mineral  resources,  are  apt  to  be  occupied  by  a  sparse  population,  little 
infuencei  by  the  outside  ivorld. 

59.  Inhabitants  of  Arid  Plateaus.  —  Because  of  their  rug- 
gedness,  coldness,  and  dryness,  arid  plateaus  are  sparsely 
settled.  In  the  West,  large  areas  of  plateau  are  almost  un- 
inhabited except  by  ranchmen,  whose  cattle  and  sheep  feed 
on  the  sparse  growth  of  grass  (Figs.  127,  128). 

Because  of  the  dryness  there  is  little  farming,  except  near 
the  mountains  where  alluvial  fans  and  level  portions  of  the 
plateau  are  irrigated  by  water  from  the  mountain  streams. 
The  bottoms  of  the  canyons  are  rarely  wide  enough  for 
farms,  and  it  is  usually  impossible  to  lead  the  water  out  for 
use  in  irris^ation. 

The  Indians  who  occupied  the  arid  plateau  of  southwestern 
United  States  farmed  by  means  of  irrigation  For  protection 
from  roaming  bands  of  more  savage  Indians,  they  often  built  their 
homes,  or  pueblos,  on  the  buttes  and  mesas,  which  they  resemble 
in  color  and  form.  From  them  they  could  look  out  over  the  coun- 
try, and  be  partly  protected  from  enemies  by  the  steepness  of 
-^he  bordering  cliffs.  Some  Indians  (Fig.  148)  still  live  in  these 
situations.  Other  Indians  lived  in  caves  in  the  cliffs,  and  still 
others  under  overhanging  ledges,  where  weather  and  wind  had 
removed  weaker  rocks  from  beneath  the  more  durable  ledges. 
The  latter  are  called  cliff  dwellers,  the  former  cave  dwellers.  These 
habitations  are  no  longer  occupied. 

Summary.  —  Arid  iilateaus  are  usually  sparsely  settled,  the  lead- 
ing occupation  being  ranching,  ivith  farming  by  irrigation  ivhere 
possible. 


86  NEfV  PRimCAL   GEOGRAPHY. 

DESERTS. 

60.  Nature  of  Deserts.  — ^  A  desert  is  a  region  in  which  few 
forms  of  life  can  find  sustenance.  Thus,  by  reason  of  cold, 
the  vast  expanse  of  ice  in  Greenland  is  a  desert  ;  indeed,  it 
is  such  a  one  that,  in  a  large  part  of  its  area,  no  animal  or 
plant  can  live.  The  term  desert  is,  however,  commonly  ap- 
plied to  those  lands  on  which  there  is  so  little  rainfall  that 
only  a  few  especially  adapted  animals  and  plants  can  live. 
About  one  fifth  of  the  land  has  an  annual  rainfall  of  less 
than  ten  inches  and  is,  therefore,  desert  ;  and  fully  as  much 
more  is  arid,  having  too  little  rain  for  agriculture. ^ 

It  is  a  mistake  to  suppose  that  no  rain  falls  in  deserts,  for 
there  is  no  land  on  the  earth  so  desert  that  it  does  not  have 
some  rainfall.  One  of  the  driest  deserts  is  in  southern  Peru, 
where,  close  by  the  Pacific,  a  period  of  seven  years  has 
elapsed  between  rains.  Nor  is  it  correct  to  imagine  deserts 
as  dreary  wastes  of  sand  and  monotonous  expanses  of  plains. 
It  is  true  that  there  is  much  drifting  sand,  and  that  most 
deserts  are  either  plains  or  plateaus  ;  but  deserts  also  have 
many  bare,  rocky  slopes,  and  even  mountains  (Figs.  150- 
152).  Where  the  mountains  rise  high  enough,  rain  falls  on 
their  slopes,  streams  flow  down  their  valleys,  and  forests 
clothe  their  sides. 

Summary.  — Deserts  are  due  to  cold,  and  to  lack  of  rain,  tJiongh 
even  the  driest  have  some  rainfall.  Most  deserts  are  ^ilains  and 
plateaus,  ivith  imich  sand,  though  there  are  also  mountains  and 
raany  hare,  rocky  slopes. 

61.  Drainage  of  Deserts.  —  With  so  little  rain  there  is  natu- 
rally little  drainage.  Most  of  the  rainfall  either  quickly 
evaporates  from  the  surface  or  sinks  into  the  soil;  but  a 
heayy  rain  is  followed  by  a  rapid  run  off,  because  there  is  little 
vegetation  to  check  the  flow  of  the  water.  Heavy  rains, 
known  as  "  cloudbursts,'^  sometimes  occur,  especially  in  the 

1  For  explanation  of  desert  climates,  see  page  281. 


PLAINS^  PLATEAUS,  AND  DESERTS,  87 

moautains  ;  and  the  water,  running  out  upon  more  level  land, 
causes  floods,  which,  however,'  quickly  subside. 

Because  of  these  sudden  floods,  it  is  dangerous  to  camp  in  a 
dried-up  stream  bed,  or  arroyo.  Kail  ways  crossing  deserts  are 
often  damaged  by  these  floods ;  crops  and  houses  are  washed  away ; 
and  vast  quantities  of  sediment  are  brought  down.  This  forms 
alluvial  fans,  often  very  stony  near  the  mountains. 

It  may  be  months  or  even  years  between  rains,  so  that  desert 
streams  are  typically  intermittent.  Those  from  the  mountains 
have  a  more  regular  flow,  and  some  have  so  large  and  steady  a 
water  supply  that  the}^  are  able  to  maintain  their  course  entirely 
across  a  desert.  Thus  the  Colorado  River  and  the  Nile,  fed  from 
distant  mountains,  flow  across  deserts  to  the  sea. 

Most  desert  streams  carry  so  little  water  that  they  lose  them- 
selves, or  waste  away,  a  few  hundred  yards,  or  a  few  miles,  fron- 
the  base  of  the  mountains  in  which  they  are  born.  Sometimes 
they  terminate  in  a  salt  marsh,  or  saline;  sometimes  in  an  alkali 
flat  (p.  169)  ;  sometimes,  when  there  is  enough  water,  in  salt  lakes. 
The  alkali  and  salt  are  brought  in  small  quantities,  dissolved  ir 
the  water,  and  left  when  it  evaporates.'  Where  salt  lakes  formerh 
existed,  and  on  the  salines  and  alkali  flats,  there  are  barren  and 
desolate  areas  of  glistening  salt  or  alkali. 

Summary.  —  Most  desert  streams  are  intermittent  and  subject  to 
occasional  Hoods;  but  some  large  rivers^  fed  amoiig  the  mountains, 
maintain  their  course  across  the  desert.  Many  streams  waste  away 
on  the  desert  and  end  in  salt  lakes,  salines,  and  alkali  flats. 

62.  Wind  Work  on  Deserts.  —  On  deserts  the  work  of  the 
wind  (Fig.  147)  is  more  important  than  that  of  water.  Small 
dust  whirlwinds  are  common  on  hot  summer  days,  and  even 
moderate  winds  drift  the  sand  and  dust  along  the  surface. 
Violent  winds  raise  the  sand  in  the  air,  causing  fierce  dust 
storms  which  obscure  the  sky  and  land,  and  even  endanger 
life.  During  such  a  wind  the  movement  of  the  sand  may 
entirely  change  the  details  of  the  land  surface.  The  finer 
dust  is  often  drifted  far  away,  dust  from  the  Sahara  having 
settled  in  central  Europe  and  on  ships  west  of  Africa-. 


88 


NEiV  PHYSICAL   GEOGRAPHY. 


It  is  this  wind  work  that  j)iles  up  the  sand  which  every  onf 
associates  with  deserts.  The  sand  is  made  of  small  rock  fragments 
weathered  from  the  cliifs  (Fig.  151),  and  brought  down  by  the 
streams.  It  is  drifted  about,  and  gathered  into  vast  areas  of  sand 
dunes,  which  are  so  difficult  to  cross  that,  wherever  possible,  caravan 
routes  carefLdly  avoid  them.  The  sand  dune  hills  may  reach  a 
height  of  several  hundred  feet,  though  usually  they  are  tnuch  lower. 


Fig.  147.  —  Ripple  marks  caused  by  wiuds  blowing  tbe  sand  about  in  south- 
western United  States,  on  the  Mexican  boundary. 

The  front  is  steep  on  the  side  away  from  the  wind,  and  the  surface 
is  rippled  with  sand  waves  (Fig.  147),  formed  by  movement  of  the 
sand  before  the  wind.  Sand  dune  hills  slowly  change  form  and  posi- 
tion, and  cities  in  central  Asia  have  been  buried  by  their  advance. 

Summary,  —  Winds  move  the  small  rock  fragments  about,  accumw- 
latirig  the  sand  in  favorable  positions,  thus  forming  belts  of  sand 
dunes  which  are  ever  changing  in  form  a7id  position. 

63.  Life  on  Deserts.  — Deserts  offer  little  incentive  to  human 
occupation.     The  barrenness  of  the  country  (Figs.  148-151) 


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PLAINS,  PLATEAUS,  AND  DESERTS.  89 

and  sparseness  of  the  population  are  unfavorable  to  the  devel- 
opment of  mineral  deposits,  and  there  is  little  opportunit} 
for  other  industries.  The  rainfall  is  too  lisfht  for  aofriculture 
without  irrigation,  and  only  a  few  parts  have  a  water  supply 
for  irrigation.  Areas  which  have  water  are  called  oases  (Fig. 
152)  ;  these  are  usually  either  scattered  springs  in  the  desert, 
or  else  places  where  streams  descend  from  mountain  canyons 
and  flow  out  upon  alluvial  fans.  A  large  stream,  like  the 
Nile  or  Euphrates,  causes  a  large  oasis  which  may  support  an 
enormous  agricultural  population. 

A  few  scattered  people  find  life  possible  in  all  the  desert  lands. 
In  the  Old  World  the  desert  jjeople  (Fig.  526)  are  nomads,  or  wan- 
derers, who  move  with  their  herds  from  oasis  to  oasis^  to  give  the 
animals  a  chance  to  feed  on  the  sparse  desert  vegetation.  Such 
a  life  of  danger  and  privation  develops  a  hardy,  warlike  people, 
with  love  of  freedom  and  a  contempt  for  the  monotonous  settled 
life  of  the  farmer.  These  people,  having  learned  how  to  use  the 
camel  (Fig.  519),  "  the  ship  of  the  desert,"  for  carrying  their  bur- 
dens, have  long  been  traders  and  caravan  leaders  across  the 
deserts.  For  centuries  the  chief  means  of  communication  between 
the  east  and  west  of  the  Old  World  was  by  caravan.  Many  of  the 
Bible  descriptions  refer  to  desert  life,  for  Palestine  is  surrounded 
by  desert  and  is  on  caravan  routes. 

Summary.  —  Except  on  the  oases,  deserts  are  unfavorable  to  settle- 
ment, being  occiqned,  in  the  Old  World,  by  a  scattered  nomadic  popu- 
lation, engaged  in  herding  and  in  caravan  trade  by  use  of  the  camel. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  —  46.  Continental  Shelf  Plains.  —  Off  Xorth 
American  coast,  —  width,  depth,  origin;  result  if  uplifted. 

47.  Coastal  Plains.  —  (a)  Origin  and  instances,  (b)  Atlantic  coastal 
plain:  extent;  structure;  artesian  wells,  (c)  Agriculture:  sandy  soil; 
higher  lands;  swamplands.  ((/)  Coast  lii^ie:  effect  of  sinking ;  fishing; 
sand  bars ;  navigation,  (e)  Rivers :  swamps ;  lakes ;  young  valleys. 
(/)  Fall  Line  :  cause ;  Indian  settlements ;  location  of  cities. 

48.  The  Russian  and  Siberian  Plains.  —  Extent;  origin;  condition  of 
drainage ;  the  tundra ;  the  .forest  belt ;  the  steppes. 


90  NEW  PHYSICAL   GEOGRAPHY. 

49.  Plains  and  Prairies  of  Central  United  States.  —  (a)  General  fea^ 
tures  :  origin;  later  changes;  elevation;  slopes;  influence  on  Mississippi. 
(b)  Great  Plains:  climate;  grazing;  agriculture;  timber,  (c)  Prairies: 
cause;  influence  on  settlement,  (d)  Mineral  deposits:  kinds;  influence 
on  manufacturing,     (e)  Other  great  plains. 

50.  Lake  Plains.  —  Lake  bottoms ;  drained  lake  bottoms ;  Red  River 
valley  plains ;  evaporated  lake  bottom  plains ;  other  classes  of  plains. 

51.  Life  History  of  a  Plain.  —  Young  plain  ;  mature  plain  ;  old  plain; 
belted  coastal  plains,  — strata,  denudation,  resuH. 

52.  Nature  of  Plateaus.  —  Association  with  mountains;  relationship  to 
plains;  elevation  of  certain  plateaus;  tilted  plateau  blocks;  lava  floods. 

53.  Sculpturing  of  Plateaus.  —  Life  history ;  effect  of  arid  climates. 

54.  Canyons. — Definition;  occurrence;  Colorado  Canyon. 

55.  Mesas  and  Buttes.  —  Mesas ;  buttes ;  tablelands. 

56.  Superimposed  and  Rejuvenated  Rivers.  —  (a)  Superimposed:  mean- 
ing; example,     (b)  Rejuvenated. 

57.  Climate  of  Plateaus.  —  Coolness;  illustrations;  arid  climate. 

58.  Inhabitants  of  Moist  Plateaus.  —  Surface  features  of  plateau  vp^est 
of  the  Appalachians ;  inhabitants;  occupations;  coalmining;  New  York. 

59.  Inhabitants  of  Arid  Plateaus.  —  Climate  ;  ranching  ;  irrigation  ; 
Indian  pueblos  ;  cliff  dwellers ;  cave  dwellers. 

60.  Nature  of  Deserts.  —  Two  causes;  extent;  rainfall;  surface  features. 

61.  Drainage  of  Deserts.  —  Rainfall;  runoff;  "cloud-bursts";  arroyos; 
effects  of  floods  ;  intermittent  streams ;  large  streams  fed  from  moun- 
tains ;  withered  streams ;  salines  ;  alkali  flats ;  salt  lakes ;  cause. 

62.  Wind  Work  on  Deserts.  —  Importance ;  sand  storms ;  source  of 
sand  ;  sand  dunes  ;  change  in  position. 

63.  Life  on  Deserts.  —  Mineral;  farming;  oases;  nomads;  camel. 
Questions.  —  46.   What  are  the  conditions  on  the  sea  bottom  off  the 

North  American  coast?     What  would  result  if  it  were  elevated? 

47.  Where  are  coastal  plains  found ?  Why?  Why  is  artesian  water 
found  in  them  ?  What  industries  are  developed  on  the  Atlantic  coastal 
plain?  What  is  the  nature  of  the  coast  line?  Why?  What  are  the 
evidences  of  youth?     What  are  the  cause  and  effects  of  the  Fall  Line  V 

48.  What  is  the  extent  of  the  Russian  and  Siberian  plains?  Yvluit  is 
their  origin  ?  What  proof  is  there  of  youth  ?  What  are  the  conditions 
in  the  northern,  central,  and  southern  portions? 

49.  What  is  the  general  condition  of  the  plains  of  central  United 
States  ?  What  are  the  conditions  on  the  Great  Plains  ?  Why  are  the 
prairies  treeless?  What  effect  has  this  condition  had?  Account  for 
the  development  of  the  central  plains  region.  Where  else  are  similar 
plains  found? 


PLAINS,   PLATEAUS,   AND  DESERTS.  91 

50.  What  has  caused  the  plains  of  the  valley  of  the  Red  River  of  the 
North?  Those  near  Great  Salt  Lake  ?  What  other  kinds  of  plains  are 
there  ? 

51.  State  the  life  histoiy  of  a  plain.     Explain  belted  plains. 

52.  How  are  plateaus  related  to  mountains?  How  do  they  differ 
from  plains  ?     What  is  the  condition  of  the  rock  strata  ? 

53.  How  does  the  life  history  of  plateaus  resemble  and  differ  from 
that  of  plains?     What  effect  has  an  arid  climate  on  sculpturing? 

54.  What  is  a  canyon  ?     Describe  the  Colorado  canyon. 

55.  Explain  mesas.     Buttes.     Account  for  the  name  tableland. 

56.  What  are  superimposed  valleys?     What  are  rejuvenated  valleys? 

57.  How  do  plateaus  affect  temperature?  Give  illustrations.  Why 
are  plateaus  often  arid  ? 

58.  What  is  the  condition  of  the  plateau  west  of  the  Appalachians  ? 
What  effect  has  this  on  the  people?  What  differences  are  there  from 
Tennessee  to  Nev7  York  ?     Why  ? 

59.  Why  are  arid  plateaus  sparsely  inhabited  ?  What  are  the  indus- 
tries ?     How  did  the  Indians  of  the  Southwest  formerly  live  ? 

60.  State  the  causes  for  deserts.  What  about  the  rainfall?  The 
surface  features  ? 

61.  Describe  the  conditions  of  drainage  in  deserts.  What  is  the 
cause  of  salt  and  alkali  deposits? 

62.  Describe  wind  work  in  deserts.  Describe  and  explain  desert 
sand  dunes. 

63.  What  are  the  industries  of  deserts?  What  are  nomads?  How 
do  they  live  ?     Of  what  importance  is  the  camel  ? 

Suggestions.  —  (1)  Make  a  coastal  plain.  In  a  shallow  dish  make  an 
irregular  land  surface  of  clay.  Have  one  portion  hilly  to  represent  land, 
the  other  part  low.  Fill  the  lower  portion  with  water.  With  a  sprin- 
kling pot  carefully  wash  some  of  the  land  into  the  depression,  then  drain 
off  the  water  with  a  siphon.  Notice  the  marginal  plain  that  is  built 
off  the  land.  It  is  a  fair  miniature  of  a  coastal  plain.  Is  it  perfectly 
ievel?  What  irregularities  are  there?  Why?  (2)  In  the  same  dish 
mold  a  basin  of  clay,  and  drop  pebbles  on  the  bottom  to  represent  hills. 
Partly  fill  with  water.  Sprinkle  clay  into  the  water,  and,  after  it  has 
settled,  draw  off  the  water.  If  clay  enough  has  been  added  the  bottom 
will  be  level,  quite  like  a  drained  lake.  What  is  the  nature  of  this  bot- 
tom? How  does  it  compare  wdth  those  described  in  the  text?  The  con- 
ditions which  existed  in  the  Great  Salt  Lake  region  can  be  imitated  by 
allowing  the  water  to  evaporate,  instead  of  drawing  it  off.  The  condi- 
tion in  the  Red  River  valley  can  be  imitated  by  making  one  side  of  the 
basin  of  packed  snow  or  ice  and  allowing  it  to  melt,  thus  draining  the  lake. 


92  NEW  PHYSICAL   GEOGRAPHY. 

(3)  Make  a  basin  similar  to  the  above,  but  use  salt  water  (dissolviiLg  salt 
in  the  water  before  pouring  it  in).  Then  allow  it  to  evaporate.  What 
is  the  result?  This  is  similar  to  the  conditions  which  have  caused  many 
beds  of  salt,  for  example,  those  of  New  York,  Michigan,  Kansas,  and 
the  Far  West.  (4)  To  make  an  artesian  well.  On  a  gently  inclined 
board  (say  at  an  angle  of  10°)  place  a  layer  of  sand  and  pebbles,  two 
inches  thick ;  cover  with  a  piece  of  thin  cotton  cloth,  or  cheese  cloth  ; 
and  then  place  on  this  a  layer  of  clay  four  inches  thick.  Extend  the  clay 
down  over  the  lower  edge  and  the  two  sides  of  the  pebble  layer,  making 
it  so  tight  that  water  will  not  seep  through  easily.  Pour  water  in  at  the 
upper  edge  of  the  pebble  layer.  Now,  near  the  lower  end  of  the  board, 
insert  a  glass  tube  six  inches  long  down  to  the  pebble  layer  (it  will  be 
well  to  leave  a  small  hole  in  the  cloth  for  this  purpose).  The  water  should 
flow  out  of  the  tube  as  an  artesian  well  does.  (5)  Make  a  small  plain  of 
clay,  sloping  in  one  direction,  and  slowly  sprinkle  it  with  a  spray  of  water. 
Watch  carefully  and  describe  every  stage  in  the  wearing  away  of  the 
plain.  (6)  Make  a  much  higher  plain,  to  represent  a  plateau,  and  note 
the  difference  between  the  wearing  away  of  the  two.  If  a  very  thin 
layer  is  made  with  a  little  plaster  of  paris  in  it  (not  too  firmly  cemented), 
buttes  and  mesas  may  be  made  by  sprinkling.  (7)  Map  studies  are  sug- 
gested in  Appendix  J. 

Reference  Books.  —  Tarr,  Physical  Geography  of  New  York  State, 
Chap.  Ill,  Macmillan  Co.,  New  York,  1902,  $3.50;  Chamberlain,  Artesian 
Wells,  5th  Annual  U.  S.  Geological  Survey,  p.  131  ;  Salisbury,  The 
Physical  Geography  of  New  Jersey,  New  Jersey  Geological  Survey,  Tren- 
ton, N.J.,  1895 ;  Abbe,  Physiography  of  Maryland,  Vol.  I,  Part  II, 
Maryland  Weather  Service,  Baltimore,  Md.,  1899;  Campbell  and 
Mendenhall,  West  Virginia  Plateau,  17th  Annual  U.  S.  Geological 
Survey,  p.  480;  Powell,  Exploration  of  the  Colorado  River  of  the  West, 
Washington,  1875  (out  of  print ;  second-hand  stores)  ;  Powell,  Canyons 
of  the  Colorado,  Flood  and  Vincent,  Meadville,  Pa.,  1895,  $10.00  ;  Dutton, 
Colorado  Canyon,  2d  Annual  U.  S.  Geological  Survey,  p.  49 ;  also  Mono- 
graph II,  U.  S.  Geological  Survey,  Washington,  D.C.,  $10.00. 


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CHAPTER  VI. 


MOUNTAINS. 


64.  Introductory.  —  Mountains  contrast  strikingly  with 
plains,  but  resemble  dissected  plateaus  in  irregularity  of 
form.  The  ruggedness  and  coldness  of  lofty  mountains 
make  them  barriers  rather  than  attractive  homes.  Mineral 
wealth  often  induces  men  to  live  among  mountains,  and,  in 
summer,  people  are  attracted  to  them  by  the  cool  climate  and 
beautiful  scenery.  But,  not  being  suited  to  extensive  agri- 
culture, mountains  are  never  densely  settled. 

These  and  other  facts  furnish  reasons  why  mountains  are 
worthy  of  study.  There  are  many  questions  o-f  interest  which 
such  a  study  will  answer.  Why,  for  example,  are  the  Alps 
so  high  and  rugged,  the  Appalachians  so  low  and  ridge-like, 
and  the  New  England  mountains  so  low  and  hilly  ?  Why  do 
rivers  sometimes  cross  mountains  in  narrow  gaps  while  other 
mountain  valleys  are  broad  and  flat-bottomed  ?  The  follow- 
ing pages  answer 
some  of  tiiese 
questions. 

65.  The  Moun- 
tain Rocks.  —  Un- 
like those  of  plains 
and  plateaus,  the 
strata  of  moun- 
tains   are    almost 

never  horizontal.  All  kinds  of  folds  and  faults  (p.  37)  are 
found.  Some  mountains,  like  many  in  the  Great  Basin,  are 
simply  faulted  and  tilted  blocks  of  strata,  with  the  layers 
inclined  in  a  single  direction  (Fig.  155).     Others,  like  the 


Fig.  155. —Fault  block  mountains. 


94  NEW  PHYSICAL   GEOGRAPHY, 

Jura  in  Switzerland,  consist  of  strata  folded  into  regular 
anticlines  and  synclines  (Fig.  168).  Still  others,  like  the 
Alps,  are  very  complexly  folded  and  faulted  (Fig.  156). 
The  strata  of  the  Appalachians  were  originally  horizontal, 


Schatlienlh        WiiidgallH--'  ^vf  iDsWaar-Massi>\"'       /' Go'ttl  ard-Maisiv  .         ""         y'esper'o  ^.Campo  Ir.ifco 

iladeranlh^-'  Orsefenth  '  >^Valle_Le»6nt.na,- 


Fig.  156.  —  Complex  folding  of  the  Alps.    The  dotted  lines  extend  the  layers  up- 
ward, as  they  would  extend  if  nothing  had  heen  removed. 

but  are  now  complexly  folded.  If  they  could  be  straightened 
out  to  their  original  condition,  they  would  occupy  fully  six 
times  as  much  area  as  now.  That  is  to  say,  120  miles  of 
rock  strata  have,  by  folding,  been  crowded  into  twenty  miles 
of  mountain. 

Such  complex  folding  often  so  alters,  or  metamorphoses,  the 
rocks  that  it  is  very  difficult  to  tell  their  original  condition 
(p.  34).  Igneous  rocks  often  cut  across  the  mountain  strata 
(Fig.  34),  and,  therefore,  one  may  in  a  short  distance  find 
many  kinds  of  rock  —  granite,  gneiss,  sandstone,  limestone, 
etc.  —  occupying  many  different  positions.  This  complexity 
gives  denudation  an  opportunity  to  sculpture  mountains  into 
many  irregular  land  forms  that  are  not  possible  on  plains  and 
plateaus. 

Summary.  —  ^fountain  rocks  are  inclined  at  various  angles  bf/ 
folding  and  faulting,  and  they  are  cdso  very  complex  in  kind.  In 
these  respects  mountains  coyitrast  strikingly  tvith  plains  and  plateaus. 

66.  Names  applied  to  Parts  of  Mountains.  —  A  mountain  system 
is  a  series  of  mountain  folds,  raised  by  the  same  uplift  and  form- 
ing a  single  group.  A  mountain  system  consists  of  minor  por- 
tions, or   ranges  (Fig.  153).     A   group  of   mouutain  systems  is 


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MOUNTAINS, 


95 


Fig.  159.  —  Diagram  to  show  mountain  ridges  where 
denudation  has  etched  inclined  hard  strata  into 
relief. 


called  a  cordillera.  For  example,  the  Cordillera  of  w-stern  United 
States  includes  four  systems,  —  the  Coast  Ranges,  the  Sierra 
Nevada-Cascade  system,  the  Basin  Range  system,  -and  the  Rocky 
Mountain  system.  Each  of  these  systems  consists  of  a  number  of 
ranges;  for  instance,  the  Rocky  Mountain  system  has  many  ranges, 
such  as  the  Wasatch  and  Uinta  ranges. 

Denudation,  wearing  away  the  ranges,  leaves  some  of  the  hard 
rocks  standing  above 
the  general  leveL  If 
these  elevated  por- 
tions are  long,  they 
are  called  ridges 
(Figs.  38,  154,  159); 
if  not  greatly  elon- 
gated, peaks  (Fig. 
157).  There  may 
be  many  peaks  and 

ridges  in  a  single  range  (Fig.  153).  More  rarely  ridges  and  peaks 
are  formed  by  folding  or  faulting  (Fig.  155). 

There  are  different  kinds  of  valleys  among  mountains.  The 
largest  of  these  are  the  broad  plateaus  between  mountain  systems. 
When  they  have  no  outlet  to  the  sea,  as  in  the  Great  Basin  of  the 
West,  they  are  called  interior  basins  (p.  22).  Smaller  basins  with- 
out outlet  are  formed  between  mountain  ranges  by  downfolding. 
Broad  valleys  in  the  Rocky  Mountains,  some  due  to  folding,  others 
to  denudation,  are  commonly  called  parks  (Fig.  165).  In  the 
Appalachians,  narrow  gorges  cut  by  streams  across  ridges,  are 
called  water  gaps  (Figs.  172,  463,  467).  A  mountain  pass  (Figs. 
158,  187)  is  a  low  portion  of  a  mountain  divide.  Passes  are  usually 
caused  by  denudation,  where  streams  head  together  on  opposite 
sides  of  a  divide.  Their  position  is  often  due  to  the  presence  of 
a  weak  rock. 

Summary.  —  The  names  cordillera,  system,  range,  ridge,  and  j^eak 
are  applied  to  mountains  or  parts  of  mountains.  The  names  interior 
basin,  j^ark,  water  gap,  and  pass  are  applied  to  mountain  valleys. 

67.  Climate  of  Mountains.  —  The  temperature  of  the  air 
decreases  1°,  on  the  average,  for  every  300  feet  of  elevation. 


96  NEW  PHYSICAL   GEOGRAPHY, 

Therefore,  high  plateaus  and  mountains  rise  into  the  cool 
upper  layer^i  if  the  air.  Indeed,  many  mountains  rise  so  high 
that  there  is  perpetual  snow  on  their  summits,  and  glaciers 
in  their  valleys.  The  line  above  which  there  is  perpetual 
snow  is  calJed  the  snow  line  (Figs.  153,  157).  Below  this  is 
a  belt  with  a  climate  too  cold  for  tree  growth.  The  line 
above  which  trees  cannot  grow  is  known  as  the  timber  line 
(Figs.  158,  166).  These  lines  are  lower  on  the  shady  than 
on  the  sunny  side  of  mountains,  and  in  the  temperate  than 
in  the  tropical  zone. 

Mountains  in  the  path  of  vnpor-bearing  winds  have  abundant 
rainfall  on  the  slopes  against  which  the  winds  blow  (p.  287).  The 
opposite  slopes,  and  the  country  beyond,  are  dry,  because  so 
much  vapor  is  lost  in  passing  over  the  mountains.  This  is  well 
illustrated  in  northwestern  United  States,  where  winds  from  the 
Pacific  cause  abundant  rain  on  the  western  slopes,  but  reach  the 
eastern  side  so  dry  that  the  country  is  arid. 

Summary. —  On  higJi  mountains  there  is  a  line,  called  the  timber 
line,  above  which  no  trees  can  grow;  higher  still  is  a  zone  of  per- 
petual snow.  Mountains  are  well  watered  on  the  side  from  ivhich 
vapor-bearing  icinds  blow,  and  often  arid  on  the  opposite  slopes. 

68.  Denudation  of  Mountains.  —  The  climate  and  great 
elevation  of  mountains  give  high  power  to  the  agents  of 
denudation.  Because  the  rivers  are  well  above  base  level, 
they  are  able  to  cut  deep  gorges  (Fig.  167)  and  canyons. 
Weathering  is  also  very  active,  especially  on  steep  slopes 
above  the  timber  line  (Figs.  51,  160),  where  there  is  little 
vegetation  to  offer  protection  to  soil  and  rock.  In  such 
situations  the'  rock  is  exposed  to  sharp  contrasts  in  tempera- 
ture between  day  and  night ;  frost  action  is  vigorous ;  and 
the  strong  winds,  heavy  rains,  and  melting  snows  all  help 
to  move  rock  fragments  down  the  steep  slopes'. 

Among  high  mountains  the  slopes  are  often  so  steep  that  the 
rock  fragments  fall  to  their  base  (Figs.  54,  183).  Some  of  this 
rock  waste  is  carried  away  by  streams,  but  very  often  more  falls 


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Fig.  161.  —  Paths  oi  avaiaucues  tiirougu  the  forest  uu  l;iii_).toii  Peak,  Colorado. 


FiQ.  162.  <—  Surface  of  the  avalanche  that  crossed  the  Simplou  Pass  road,  coming 

4owu  the  valley  m  the  background. 


MOUNTAINS.  97 

than  can  be  thus  removed.  In  time  this  forms  a  mantle  of  rock 
waste,  or  talus  (Figs.  66,  160),  which  covers  the  lower  slopes, 
and,  by  its  smooth,  curving  outline,  frrms  a  striking  contrast  to 
the  rugged,  irregular  slopes  above.  As  the  talus  grows,  its  slope 
becomes  more  gentle,  till  rocks  no  longer  roll  down  over  it. 
Then  the  decay  of  the  fragments  forms  a  soil  in  which  trees  may 
grow  and  on  which  farms  may  be  located.  Where  wet  weather 
streams  descend  the  mountain  sides,  these  talus  slopes  grade  into 
steep  alluvial  fans  and  debris  cones  (Figs.  109,  160). 

At  all  times  small  fragments  of  rock  are  falling  from  the  steep 
mountain  slopes ;  but,  in  addition,  there  is  an  occasional  fall  of 
large  masses,  forming  an  avalanche  (Fig.  161)  or  a  landslide.  In 
an  avalanche  thousands,  and  sometimes  millions,  of  tons  of  rock, 
mingled  perhaps  with  ice,  come  tearing  down  the  mountain  side, 
destroying  everything  in  their  course.  Rivers  are  dammed,  vil- 
lages destroyed,  and  roads  ruined.  In  the  spring  of  1901  an 
avalanche  of  rock  and  ice  from  an  Alpine  vf^lley  descended  across 
the  road  which  Napoleon  built  over  the  Simplon  Pass  (Fig.  162). 
It  ruined  a  mile  or  two  of  the  road  and  utterly  destroyed  a  mountain 
village.  About  a  century  before,  a  similar  avalanche  occurred  in 
the  same  place.  Mountains  supply  many  instances  of  such  destruc- 
tive landslides.  They  are  usually  started  by  frost,  or  by  the  effect 
of  rain  or  melted  snow,  which  saturates  the  soil  or  rock,  making  it 
so  heavy  that  it  can  no  longer  stand  in  its  position. 

As  a  result  of  rapid  denudation,  acting  on  the  complex  rocks» 
mountains  are  cut  into  a  great  variety  of  rugged  forms, — 
peaks,  ridges,  precipices,  gorges,  and  passes.  There  are  peaks 
almost  impossible  to  scale,  some  so  steep  and  sharp-pointed 
that  they  are  called  *' needles"  and  "horns"'  (Fig.  157); 
there  are  ridges  that  no  roads  cross ;  and,  in  fact,  a  surface 
often  so  rugged  that  large  areas  are  uninhabited. 

Summary.  —  River  erosion  and  tveatheriiig  are  very  active  among 
mountains,  especially  above  the  timber  line.  Mock  fragments,  falling 
from  steep  slopes,  accumidate  at  their  base  as  talus,  debris  cones,  and 
alluvial  fans;  and  occasioncdly  larger  masses  descend  as  avalanches, 
By  this  rapid  denudation  high  mountains  are  made  very  rugged. 

H 


98  NEW  PHYSICAL   GEOGRAPHY. 

69.  Resemblance  between  Mountains  and  High  Plateaus.  —  Some 
plateaus  are  more  elevated  than  many  high  mountain  peaks ;  it 
is  only  very  lofty  mountains  that  rise  higher  than  10,000  feet, 
and  yet  there  are  plateaus  which  reach  that  level.  These  high 
plateaus  are  often  so  carved  by  vigorous  denudation  as  to  closely 
resemble  mountains  (Fig.  146).  They  are,  in  fact,  sometimes  called 
mountains. 

The  Catskill  Mountains,  for  example,  are  not  mountains  in  the 
true  sense,  but  dissected  plateaus.  In  the  Catskills,  denudation 
has  carved  out  peaks  and  deep  valleys  with  precipitous  sides;  but 
the  nearly  horizontal  strata   prove  that  they    were   uplifted   as 


Fig.  163.  —  A  section  showing  folded  mountain  strata  (on  the  right)  grading  into 
the  horizontal  strata  of  a  plateau  (on  the  left).  Compare  the  two  portions 
in  ruggedness  and  elevation. 

plateaus,  not  as  mountain  folds.     Such  mountain-like  plateaus  are 
usually  near  mountains,  and  gradually  merge  into  them  (Fig.  163). 

Summary. —  Vigorous  denudation  so  scidptures  high  lolateaus, 
like  the  Catskills,  as  to  make  them  resemble  mountains  in  rugged- 
ness ;  hut  their  strata  are  horizontal. 

70.  Distribution  of  Mountains. — Although  mountains  are 
typical  of  continents,  there  are  ranges  in  the  open  ocean  ;  for 
example,  the  New  Zealand  and  Hawaiian  islands.  The  latter 
are  volcanoes  rising  from  the  crest  of  a  submarine  mountain 
fold,  having  a  length  of  1500  miles.  There  are  many  other 
ranges  in  the  ocean,  especially  in  the  Soutli  Pacific. 

Mountains  are  common  at  or  near  the  border  of  continents 
(Figs.  20-27).  They  sometimes  fringe  the  coast,  as  in  the  case 
of  the  Kurile,  Japanese,  and  Philippine  islands,  and  the  East 
and  West  Indies.  Mountain  chains  also  extend  from  the  land 
into  the  sea,  forming  peninsulas  ;  for  example,  the  peninsulas 
of  Lower  California,  Kamchatka,  Malay,  Greece,  and  Italy. 
In  other  places  mountain  systems  form  the  very  border  of  the 
continents,  rising  directly  out  of  the  sea.     Such  a  condition 


MOUNTAINS.  99 

is  well  illustrated  by  the  Coast  Ranges  of  western  North 
America  and  the  Andes  of  South  America. 

Mountains  are  also  found  far  from  the  coast;  for  example, 
the  Appalachians,  Rocky  Mountains,  Sierra  Nevada,  and  the 
mountains  of  central  Europe  and  Asia.  But  most  mountains 
of  the  interior,  when  first  formed,  rose  from  the  sea. 

A  large  number  of  the  mountain  systems  extend  from 
north  to  south  (Figs.  20-25).  It  is  to  this  fact  that  several 
of  the  continents  owe  their  shape,  —  that  of  a  triangle,  with 
the  long  direction  from  north  to  south  (p.  23).  There  are, 
however,  many  ranges  running  east  and  west,  especially  in 
Asia  and  Europe  (Figs.  26,  27).  No  regular  law  has  thus 
far  been  discovered  regarding  the  distribution  of  mountains. 

Summary.  —  Mountains  occur  on  continents,  both  in  the  interior 
and  along  the  border,  where  they  fonn  chains  of  islands,  peninsulas^ 
and  systems  ivhich  rise  at  the  very  margin  of  the  land.  They  also 
form  island  chains  in  the  open  ocean.  Some  extend  north  and  south, 
others  east  and  west. 

71.  Cause  of  Mountains.  —  The  explanation  of  mountains  most 
widely  accepted  is  that  of  contraction  (p.  20).  As  the  heated 
interior  of  the  earth  cools  and  shrinks,  the  cold  crust  settles; 
but  it  cannot  fit  the  constantly  shrinking  interior  without  wrin- 
kling. This  causes  mountains,  which  are  wrinkles  in  the  earth's 
crust.  You  can  illustrate  this  by  covering  a  ball  with  a  thick 
flannel  cover  a  little  too  large  for  the  ball,  then  trying  to  press  it 
down  on  the  ball.     Some  parts  of  the  cloth  must  wrinkle. 

There  is  evidence  that  mountain  folding  has  occurred  again 
and  again  in  the  same  place  ;  also  that  this  growth  has  been  slow. 
Several  times,  mountain  systems  have  risen  in  eastern  and  western 
United  States  ;  but,  in  the  plains  between,  there  has  been  practi- 
cally no  mountain  formation  at  any  period.  The  same  is  true  of 
other  parts  of  the  earth. 

Summary.  —  Mountains  are  wrinkles  of  the  earth's  crust,  caused 
by  its  settling  on  the  cooling  and  contracting  interior.  They  have 
been  formed  slowly  and  by  successive  uplifts. 


100 


NEW  PHTSZCAL   GEOGRAPHY, 


72.  Types  of  Mountains.  —  Perhaps  the  simplest  type  of 
mountain  is  that  in  which  a  block  of  strata  has  been  up- 
lifted, along  a  fault  plane,  and  tilted  (Fig.  155).  Such  a 
mountain  has  one  moderate  and  one  steep  slope,  while  the 
crest  is  a  ridge  parallel  to  the  fault  plane.  Mountains  of 
this  type  are  found  in  southern  Oregon  and  other  parts 
of  the  Great  Basin.  These  tilted  block  mountains  may  reach 
a  height  of  4000  or  5000  feet,  a  width  of  10  to  20  miles,  and 
a  length  of  50  to  100  miles. 

Another  simple  mountain  typs  is  the  dome,  in  which  the 
strata  have  been  raised  by  the  intrusion  of  lava  (p.  127).     In 


eORMAT   A   CO.,    N.V. 


Fig.   164.  —  The  Henry  Mountains,  11,000  feet  high,  with  the  dome  restored  as  it 
would  i^robably  exist  if  denudation  had  removed  none  of  the  strata. 

such  a  mountain  there  is  no  ridge,  but  a  central  area  from 
which  the  surface  slopes  in  all  directions.  This  type  is  illus- 
trated by  the  Henry  Mts.  (Fig.  164)  and  others  in  the  West. 
A  third  simple  type  is  the  evenly  folded  mountain,  illus- 
trated by  the  Swiss  Jura  (Fig.  168)  and  parts  of  the  Appa- 
lachians. When  such  mountains  are  formed  the  surface  is 
thrown  into  a  series  of  regular  waves,  like  the  waves  of  the  sea, 
the  anticlines  forming  mountain  ridges,  the  synclines,  valleys 


i^io.   Loo. —  A  park,  or  broad,  open  mountain  valley  in  the  Rocky  Mountains. 

Sultan  Mountain  is  in  the  distance. 


Fig.  16(3.  —  The  timber  line  on  Alpine  Pass  in  the  Rocky  Moimtains  of  Colorado. 


Fig.  167.  —  A  deep,  narrow  gorge  in  the  Ali)S.  Tliere  are  pot  holes  jusi  above  the 
path  on  the  left,  showing  that  the  stream  bottom  was  once  at  that  level. 
This  gorge  is  being  rapidly  deepened. 


MOUNTAINS. 


101 


(Fig.  168).  When  denudation  cuts  deeply  into  these,  as  in 
the  Appalachians,  each  hard  layer  is  left  as  a  ridge  (Fig.  172). 
Mountains  whose  strata  are  greatly  contorted  (Fig.  156) 
and  metamorphosed,  with  much  igneous  rock,  have  a  far  less 
simple  form.  De- 
nudation, discov- 
ering differences 
in  the  rocks,  sculp- 
tures them  into 
very  irregular  and 
rugged  outlines. 
The  Rockies  and 
Alps  (Figs.  153, 
157, 165)  are  types 
of  such  mountains. 


Fig.  168. — Folds  of  the  Jura  in  Switzerland,  showiuj* 
streams  paraUel  to  the  folds  and  crossing  them  in 
deep  vallej's. 


Summary, — TJiere 
are  simple  faulted 
block  mountains  ; 
domes  raised  by  the 
intrusion  of  lava;  evenly  folded  mountci'^.s;  and  very  complexly 
folded  mountains.  The  latter  are  carved  in*e  very  irregular  and 
rugged  forms. 

73.  Life  History  of  Mountains.  —  Let  us  assume  that  the 
strata  of  a  plain  are  being  folded  to  form  a  mountain  system. 
As  the  strata  slowly  bend,  the  surface  becomes  irregular  ; 
and,  when  the  .strain  becomes  too  great,  the  rocks  slip  along 
fault  planes.  This  jars  the  earth,  forming  earthquake 
shocks,  which  may  Vie  very  severe.  Through  the  deeper 
fissures,  lava  may  rise,  building  volcanic  cones.  Such  earth- 
quakes and  volcanoes  are  common  in  regions  of  grcwing 
mountains  (pp.  125,  132). 

From  the  very  first  the  rising  land  is  attacked  by  J:be 
agents  of  denudation  ;  but  this  attack  increases  as  the  moun- 
tains grow  higher.     Since  the  mountains  are  not  worn  dowo 


102  NEW  PHYSICAL   GEOGBAPBT. 

as  rapidly  as  they  are  elevated,  they  continue  to  grow  higher, 
reaching  above  the  timber  line  and  even  into  the  zone  of 
perpetual  snow.     Then  glaciers  extend  down  the  valleys. 

Down-folding  forms  broad  valleys  between  the  ridges  ;  and 
streams  cut  narrow  gorges  across  them.  Tlie  durable  rocks 
are  etched  out  into  ridges  and  peaks,  the  weak  rocks  are 
cut  away,  forming  valleys  and  passes.  In  this  stage  the 
surface  is  so  irregular  that  few  people  are  able  to  live  among 
the  mountains.  Such  mountains,  illustrated  by  those  of 
western  North  and  South  America,  the  Himalayas,  and  the 
Alps,  are  young  mountains.  Find  pictures  of  young  moun- 
tains in  this  chapter. 

The  time  comes  when  uplift  ceases  :  but  denudation  con- 
tinues to  broaden  the  valleys  and  lower  the  peaks  and  ridges. 
As  the  mountains  are  lowered,  glaciers  disappear,  and,  in 
time,  even  the  highest  peaks  may  come  below  the  timber  line. 
Such  mountains,  which  have  lost  the  ruggedness  of  youth, 
may  be  called  mature  ;  the  Appalachians  and  the  mountains  of 
New  England,  Norway,  and  Scotland,  are  examples  (Figs.  170, 
172,  188,  189,  192,  193,  455).  Their  slopes  are  forested, 
their  valleys  tilled. 

Further  lowering  may  continue  until  the  mountains  are 
reduced  to  a  series  of  low,  rolling  hills  ;  or,  further  still, 
to  a  surface  almost  as  level  as  a  plain.  Such  a  surface  is 
known  as  a  peneplain  (almost  plain)  (Fig.  171).  The  moun- 
tains are  then  old^  and  are,  like  plains,  adapted  to  dense 
settlement.  New  York  City,  Philadelphia,  Baltimore,  and 
Washington  are  situated  on  such  old,  worn-down  mountains. 
These  ancient  mountains,  known  as  the  Piedmont  belt,  extend 
from  New  England  to  Alabama,  east  of  the  Appalachians. 

After  being  worn  to  low  relief,  a  mountain  region  may  be  reele- 
vated,  and  caused  to  start  on  a  new  life  history,  as  has  been  the 
case  with  the  Appalachians.  Then  denudation  may  etch  the 
ridges  of  hard  rock  into  relief  again,  and  form  broad  valleys 
where  the  strata  are  weak  (Figs.  172,  173,  192,  193).     The  broad 


FiQ.  169.  —  A  rugged  cliff,  ridge,  aud  penis,  m  me  Alps,  carved  out  by  the  active 
denudation  in  these  young  mountains.  The  house  is  a  summer  hotel  f«r 
tourists. 


Fig.  170. —  Mature  mountains  in  the  Lake  District  of  northwestern  England 
made  famous  by  the  poet  Wordsworth.    The  lake  is  Derwentwatet 


Fig.  171. — The  upland,  or  •"penopluiu,"  of  iNew  ±!:iiglana  ;  a  worn-down  moun- 
tain region,  uplifted  again  so  that  the  streams  have  had  new  power  given 
them  (rejuvenated).  This  has  enabled  the  streams  to  sink  their  valleys 
into  the  "  peneplain." 


>^-\^ 

t-^- 


.&\!£/. 


K>A:x?::i  t'. 


Fig.  172.  —  Hidges  of  the  Appalachian  Mountains  crossed  by  the  Susquehanna. 

(Harden's  model.)     (See  also  Fig.  192.) 


ASW? 


V 


S   ") 


Fig.  \1'A.  —  To  illustrate  the  origin  of  the  Appalachian  ridges.  The  mountains 
were  worn  down  to  low  relief,  as  in  the  left-hand  figure ;  then,  after  uplift, 
the  ridges  were  etched  out.  The  streams  crossing  them  have  cut  water 
gaps,  while  broad  valleys  have  been  developed  between  the  ridges  in  the 
weaker  strata. 


Fig.  174.  —  The  left-hand  figure  shows  two  anticlinal  ridges  each  cut  into  for  a  short 
distance  by  a  stream.  As  the  streams  cut  deeper  and  grow  longer,  they  reach 
below  a  hard  layer  (the  darkest  one  in  the  diagram),  which,  because  of  its 
hardness,  is  left  standing  as  a  ridge  on  each  side  of  the  valley  (right-hand 
figure).  The  law  of  monoclinal  shifting  will  cause  these  ridges  to  retreat 
away  from  the  stream,  thus  broadening  the  valleys  in  the  anticlines,  and  at 
the  same  time  narrowing  the  synclinal  valleys.     (See  also  Fig.  179.) 


Fig.  175.  — In  the  left-hand  figure  a  stream  heads  on  a  divide  and  flows  in  a  short 
course  toward  the  right  to  the  sea.  This  steep  slope  gives  it  power  to 
gradually  eat  backward  until  it  reaches  a  stream  having  a  long,  roundabout 
course  to  the  sea.  It  then  captures  the  stream  and  leads  it  out  to  the  sea  by 
the  shorter  course,  as  shown  in  the  right-hand  fij.'-ure. 


Figs.  174,  175,  177,  178,  and  179  are  introduced  for  da&s  study,  supplementary  to 

the  text. 


MOUNTAINS,  103 

valleys  are  well  settled  (Fig.  466),  but  the  ridges  are  too  rough 
and  rocky  for  farming,  and  are  often  timber-covered  (Figs.  85, 
467).  Where  streams  leave  the  broad  valleys  to  cross  the  ridges 
of  hard  rock,  they  flow  in  narrow  gorges,  or  ivater  gaps  (Figs.  178, 
463, 467),  because  there  has  not  been  time  for  weathering  to  broaden 
valleys  in  so  hard  strata. 

Summary.  —  As  mountains  rise,  the  effect  of  denudation  increases, 
and  young  mountains  are  therefore  made  very  rugged.  Mature 
mountains  have  been  lowered  and  the  valleys  broadened;  and.  old 
mountains  are  still  further  lowered,  and  perhaps  even  reduced  to 
1  peneplain.  Uplift  alloivs  denudation  to  again  etch  the  hard  strata 
into  relief. 

74.  The  Drainage  of  Mountains.  —  In  early  stages,  in  con- 
sequence of  the  slopes,  numerous  short  streams  flow  down 
the  mountain  sides  in  gorges ;  and  longer  streams  follow  the 
broad  valleys  between  the  mountain  folds.  Here  and  there 
the  main  streams  cut  deep  gorges  across  low  points  in  the 
folds  (Fig.  168).  In  such  consequent  mountain  drainage 
there  are,  at  first,  numerous  lakes  held  up  by  the  mountain 
iams.  These,  however,  are  soon  filled  with  sediment  brought 
oy  tne  mountain  torrents.  A  slight  renewal  of  mountain 
movement  may  warp  the  valleys  and  form  new  lake  basins 
(Fig.  296).  Some  of  the  Alpine  lakes,  such  as  Geneva,  are 
thus  explained. 

If  the  elevation  of  the  land  ceases,  the  valleys  pass  through 
the  stages  of  youth,  maturity,  and  old  age.  But  the  great 
elevation,  and  the  hard  and  complex  nature  of  the  mountain 
rocks,  make  the  life  history  of  a  river  valley  in  mountains 
longer  than  in  plains  and  in  most  plateaus. 

The  wearing  away  of  the  weak  rocks  leaves  the  hard  strata 
standing  as  divides  (Figs.  38,  154,  169).  As  the  surface 
slowly  wears  down,  the  divides  still  remain  on  the  more 
durable  strata.  These  mountain  strata  usually  incline,  or 
dip ;  and,  as  they  are  slowly  worn  away,  their  crests,  that  is 
the  divides,  not  only  become  lower,  but  shift  to  one  side 


104 


NEW  PHYSICAL   GEOGRAPHY, 


(Fig.  176).  This,  called  the  law  of  monoelinal  shifting^  may 
be  stated  as  follows  :  As  denudation  lowers  a  region  of  inclined 
strata^  the  divide  migrates  in  the  direction  of  the  dip. 

Mountain  divides  may  migrate  for  other  reasons  (Figs.  175, 
177,  178).     Thus,  two  streams  heading  on  the  same  divide 

are  constantly  bat- 
tling for  drain- 
age area,  and 
the  stronger  one 
pushes  the  divide 
back  into  the 
territory  of  its  op- 
ponent. If  it  suc- 
ceeds in  robbing 
its  opponent  of 
its  headwaters,  it 
is  called  a  river 
pirate.  There  are 
various  reasons 
why  one  stream 
may  have  more 
power  than  another  :  one  may  have  more  rainfall ;  or  it  may 
have  a  shorter  and  steeper  slope ;  or  it  may  have  only  weak 
strata  to  remove  while  its  opponent  struggles  with  hard  strata. 

There  are  nmnerous  illustrations  of  such  migration  of  divides. 
In  the  Catskills,  for  example,  the  streams  descending  the  steep 
eastern  slope  to  the  Hudson  have  pushed  the  divide  backward  and 
captured  the  headwaters  of  streams  that  have  a  long,  gentle 
slope  (Fig.  177).  The  Appalachian  rivers,  —  the  Potomac,  Sus- 
quehanna, Delaware,  etc.,  —  which  cross  ridge  after  ridge  (Figs.  172, 
192),  are  believed  to  have  slowly  eaten  their  way  across  the  moun- 
tains by  headwater  erosion  and  river  capture.  Wind  gaps  of  the 
Appalachians  are  also  caused  by  river  capture  (Fig.  178). 

Summary.  —  Consequent  moitntain  streams  flow  down  the  moun- 
tain sides,  along  the  valleys  of  folding  and  across  the  ridges.     They 


Fig.  176.  —  To  illustrate  the  migration  of  divides.  A 
hard  layer  A  forms  a  divide  ridge.  When  the  sur- 
face has  heen  worn  down  to  the  line  CO  (upper 
figure)  the  ridge  A  will  have  migrated  to  the  right, 
as  shown  in  the  lower  figure.  See  also  Figs.  174, 179. 


Fig.  177. — The  headwaters  of  a  tributary  (left-hand  figure)  rise  on  a  highland 
and  flow  a  long  distance,  in  a  roundabout  course,  to  reach  the  main  stream. 
Two  short  streams  head  in  the  same  region,  but  flow  in  steep  courses  to  the 
main  stream.  This  gives  them  power  to  eat  back  at  the  divide  and  rob 
the  long  tributary  of  some  of  its  headwaters  (right-hand  figure).  This  condi- 
tion is  somewhat  like  that  in  the  Catskills.  Note  that  the  tributaries  of  the 
captured  streams  join  in  barb  fashion. 


Pig.  178.  —  In  the  left-hand  figure  two  streams  cross  a  mountain  ridge  of  hard 
rock.  A  tributary  of  the  upper  one  heads  back  nearly  to  the  point  where  the 
lower  one  turns  to  cross  the  ridge.  For  some  reason  (perhaps  greater  volume) 
the  upper  stream  has  more  power  to  cut  into  the  ridge,  thus  deepening  its 
valley.  This  gives  to  its  tributary  a  slope  which  permits  it  to  gradually  eat 
backward  until  it  taps  the  lower  stream,  drawing  it  off  through  the  upper 
water  gap.  This  leaves  a  wind  gap  where  the  lower  stream  formerly  crossed 
the  ridge  (right-hand  figure) . 


Fig.  179. —  The  process  of  raonoclinal  shifting,  illustrated  in  Figs.  174  and  176,  is 
carried  farther  in  this  diagram.  In  the  upper  diagram  there  are  four  streams, 
A,  B,  C,  and  D  ;  A  and  C  in  small  valleys  in  the  anticlines,  B  and  D  in  broad 
synclinal  valleys  caused  by  down  folding.  They  are  consequent  on  the  moun- 
tain form.  In  the  middle  figure  there  is  little  change,  excepting  that  the  anti- 
clinal valleys  have  been  lengthened  and  deepened,  this  being  possible  because 
they  are  so  high  that  the  streams  have  much  power,  while  the  synclinal 
streams  are  held  back  in  their  work  by  lakes  (not  shown  here)  and  hard 
strata.  The  lower  figure  represents  a  much  later  stage,  in  which  the  surface 
has  been  greatly  worn  down.  Monoclinal  shifting  has  pushed  the  divides 
away  from  the  anticlinal  streams  (Fig.  174),  therefore  broadening  their  valleys 
and  narrowing  the  synclinal  valleys.  This  has  robbed  the  synclinal  streams  of 
water,  and  consequently  weakened  them,  while  it  has  increased  the  power  of 
the  anticlinal  streams.  As  a  result,  the  conditions  have  been  reversed  from 
the  first  stage,  and  the  anticlinal  streams,  A  and  C,  flow  in  broad,  deep  val- 
leys, while  the  synclinal  streams  are  in  high,  narrow  valleys,  on  the  tops  of 
synclinal  mountains.    Instances  of  this  change  are  found  in  the  ADoalachiaus. 


Fig.  180.  — The  lower  slopes  of  the  Alps  along  the  deep  valley  occupied  by  Lake 
Como.    These  slopes  are  cultivated,  growing  olives  and  grapes,  and  towns 
cling  to  the  mountain  base  wherever  there  is  enough  level  land,  especially 
.on  the  stream  deltas  (Fig?.  107,  297). 


Fig.  181.  —  The  high,  snow-covered  slopes  of  the  Jungfrau  in  the  Alps,  showing 
summer  pasturage  above  the  timber  line,  and  up  to  the  very  edge  of  i 


glacier. 


Fig.  182. — An  Alpine  valhj^and  village,  from  which  rise  the  barren,  rocky  moun- 
tain slopes,  down  which  rock  waste  is  streaming,  forming  alluvial  fans. 


1 

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?IG.  183.  — The  bare,  rocky  slopes  of  the  high  Alps,  among  which  men  do  not 
live.    The  houses  are  hotels,  open  only  for  two  or  three  montlis  in  summer. 


MOUNTAINS,  105 

are  likely  to  be  interrupted  by  lakes.  Slowly  they  pass  through  youth, 
maturity,  and  old  age,  unless  interrupted  by  renewed  mountain  growth. 
TJie  divides  change  position  by  the  law  of  monoclinal  shifting,  and  by 
headwater  ei'osion.  In  the  latter  case  the  more  favorably  situated 
streams  capture  the  headwaters  of  opponent  streams. 

75.  Settlement  of  Mountains.  —  The  soil  and  climate  of 
mountains  are  usually  unfavorable  to  agriculture,  and,  in  many 
cases,  absolutely  forbid  it.  Large  areas  are  even  unfit  for  the 
growth  of  forests.  For  these  reasons  mountains  are  usually 
sparsely  settled  (Figs.  157,  158,  183,  185). 

The  relation  of  mountains  to  settlement  is  well  illustrated 
by  the  Alps,  which  rise  in  the  midst  of  a  densely  populated 
land,  —  Italy  on  the  one  hand,  France  and  Germany  on  the 
other.  If  we  were  to  cross  the  Alps  from  the  Italian  side, 
this  is  what  we  should  see  :  first  a  level  plain,  the  Po  valley, 
dotted  with  farms  and  villages,  and  densely  settled.  As  the 
land  becomes  irregular  in  the  foothills,  there  are  fewer 
people  ;  and,  when  the  mountains  are  reached,  large  areas  are 
found  with  a  surface  too  rocky  for  cultivation  (Figs.  107, 
180).  Wherever  there  is  soil  enough,  however,  vineyards  and 
groves  of  olive  and  mulberry  trees  are  seen  on  the  valley  sides. 

Higher  up,  where  the  climate  is  cooler,  the  olive,  mulberry, 
and  grapes  no  longer  grow  (Figs.  153,  182).  There  small 
grain-fields  and  pasture  lands  are  interspersed  with  rocky 
cliffs  and  forested  areas,  in  which  the  chestnut  is  a  common 
tree.  Still  higher,  where  the  climate  is  that  of  the  cold 
temperate  zone  (Fig.  109),  evergreen  trees  prevail,  and  only 
the  hardiest  grains  can  be  raised.  Most  of  the  land  that  has 
soil  enough  is  used  as  pasture,  and  cows  and  goats  are  raised 
in  large  numbers.  Between  the  timber  line  and  the  snow 
line  there  is  an  area  on  which  no  crops  can  be  raised,  but 
where  the  pastures  support  herds  of  cows  and  goats  for  a 
month  or  two  in  summer  (Fig.  181).  Above  this  is  a  wild, 
dreary  mass  of  snow,  rock,  and  ice,  where  no  one  can  find 
sustenance  (Figs.  157,  182,  183). 


106 


NEW  PHYSICAL   GEOGRAPHY 


Summary.  —  Mountains  are  sparsely  settled.  Agriculture  may 
flourish  at  the  base,  hut  the  ai^ea  suitable  to  cultivation  becomes 
S7naller  the  higher  one  goes,  and  the  climate  more  and  more  unfavor- 
able, until,  at  the  snow  line,  a  barren  area  of  snoiv  and  rock  is 
reached  in  which  there  are  no  inhabitants. 

76.  Mountains  as  Barriers.  —  Mountains  are  barriers  to  the 
passage  of  animals,  plants,  and  men.  On  a  plain,  animals 
and  plants  spread  freely ;  but  the  ruggedness  and  coldness  of 
mountains  check,  and  in  many  cases  prohibit,  the  passage  of 
animals  and  the  spread  of  plants.  Even  the  passes  of  high 
mountains,  like  the  Alps,  have  deep  snow  until  summer. 

The  low  Appalachians  served  as  a  barrier  to  the  westward 
spread  of  the  early  colonists  (p.  308).  The  Alps  (p.  388) 
have  always  been  an  obstacle  to  man,  being  crossed  only 
with  difficulty  and  along  the  few  passes.  The  Himalayas 
(p.  388)  are  an  even  more  effective  barrier ;  and  the  Pyrenees 

are  so  excellent 
a  barrier  that 
they  serve  as  the 
boundary  line  be- 
tween two  coun- 
tries. Name  other 
cases  where  moun- 
tains  serve  as 
boundary  lines. 

In  the  past  cen- 
tury men  have  found 


Fig.  184.  —  A  railway  crossing  the  Andes  of  Peru. 
There  are  three  levels  here,  as  in  the  St.  Gothard 
railway  (Fig.  186). 


means  of  reducing 
the  difficulties  of 
crossing  mountains. 


carnage 


Excellent 

roads,    rising  with 

gentle  slope  by  great 

sweeping  curves,  now  cross  the  principal  Alpine  passes  (Fig.  185). 

In  places  where  snow-slides  and  avalanches  are  common,  the  roads 


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Fig.  187.  —  A  summer  hotel  on  a  pass  near  Gnndelwald  in  the  Alps.     The 
mountain  in  the  distance,  on  the  right,  is  the  Wetterhorn. 


Fig.  189.  —  The  forest-covered  slopes  of  the  White  Mountains  of  Xew  Hamp 

shire,  a  famous  summer  resort. 


FiQ.  190.—- Silverton,  Col.,  a  mining  town  in  a  Rocky  Mountain  valley.    The 
timber  line  is  seec  on  the  mountain  slope. 


MOUNTAINS.  107 

are  covered  and  protected  by  avalanche  sheds.  Railways  cross  even 
the  lofty  Rocky  Mountains  (Fig.  471),  Andes  (Fig.  184),  and  Alps 
(Fig:  186).  They  pass  up  the  valleys  as  far  as  they  can  (Figs.  57, 
QQ>),  curving  about,  first  on  one  side,  then  on  the  other ;  crossing 
deep  gorges  by  lofty  bridges ;  tunneling  the  rock,  even  by  curved 
tunnels ;  and  finally,  when  it  is  no  longer  possible  to  climb 
higher,  plunging  through  a  great  tunnel  into  the  very  heart  of 
the  mountain.  The  St.  Gothard  tunnel  is  nine  and  one  fourth 
miles  long;  the  Simplon  tunnel,  farther  west,  is  even  longer. 

Summary.  —  Tlie  ruggedness  and  coldness  of  mountains  make  them 
harriers  to  the  spread  ofjylants,  animals,  and  man.  Now,  Giving  to  the 
building  of  roads  and  railways,  mountaiyis  are  far  less  important 
harriers  than  formerly, 

77.  Mountains  as  Summer  Resorts.  ^ —  The  cool  summer  climate 
and  the  wild  and  beautiful  scenery  attract  many  people  to  moun- 
tains. The  numerous  mountain  lakes  which  offer  opportunities 
for  boating  and  fishing,  and  the  hunting  on  the  forest-covered 
mountain  slopes,  are  further  attractions.  The  mountains  of  New 
England  (Fig.  189),  the  Adirondacks  (Fig.  188)  and  Catskills  of 
New  York,  and  the  Appalachians  are  visited  each  year  by  large 
numbers  of  people.  But  in  winter  they  are  cold,  snow-covered, 
and  nearly  deserted. 

The  Alps,  the  wildest  and  most  beautiful  of  European  moun- 
tains, have  come  to  be  the  greatest  summer  resort  in  the  world. 
In  the  small  country  of  Switzerland,  which  is  only  one  third  the 
size  of  Pennsylvania,  there  are  thousands  of  summer  hotels.  At 
every  point  where  many  tourists  are  likely  to  go,  even  on  moun- 
tain trails  far  from  wagon  roads,  a  hotel  is  sure  to  be  found 
(Figs.  169,  183,  187).  In  the  height  of  the  season  most  of  these 
hotels  are  full  to  overflowing  with  tourists  from  all  parts  of 
Europe,  in  fact,  from  all  the  world.  One  of  the  leading  industries 
of  Switzerland  is  the  entertainment  and  care  of  these  visitors. 

Summary.  —  TJie  climate,  scenery,  hoating,  fishing,  and  hunting 
attract  people  to  the  mountains  for  a  vacation. 

78.  Mountains  as  Timber  Reserves.  —  Mountain  slopes  are 
so  often  unsuited  to  agriculture  that  in  many  places  the  forest 


108 


NEIV  PHYSICAL   GEOGRAPHY. 


remains  (Figs.  85, 188, 189).  About  one  fifth  of  the  surface 
of  Norway  is  forest-covered,  and  much  of  the  remainder  is 
either  too  higli  or  too  rocky  for  trees  to  grow.  The  moun- 
tains of  eastern  and  western  United  States  still  have  great 
timber  resources  and  are  the  seats  of  important  lumber 
industries. 

Summary.  —  Mountains  are  important  timber  reserves,  because 
agriculture  has  not  demanded  the  removal  of  the  forests, 

79.  Mineral  Wealth  of  Mountains.  —  The  Alps  have  little 
valuable  mineral;  but  the  mountains  of  eastern  and  western 
United  States,  and  many  other  lands,  are  very  rich  in  mineral. 
In  the  West,  gold,  silver,  lead,  and  copper  are  most  impor- 
tant; but  zinc,  iron,  coal,  and  building  stones  are  also  found. 
In  the  mountains  of  eastern  United  States,  coal,  iron,  and 
building  stones  are  the  leading  mineral  products. 

The  presence  of  metal  has  attracted  many  people  to  mountain 
regions,  where  otherwise  there  would  be  only  a  sparse  population 
of  farmers,  herders,  hunters,  and  lumbermen.  In  rugged  moun- 
tain valleys,  and 
on  arid  mountain 
slopes,  cities  with 
thousands  of  inhab- 
itants have  quickly 
grown     up     around 


mining  centers. 

Mineral  beds  and 
veins  are  revealed 
by  folding  of  the 
strata  and  erosion  of 


Fig.   191.  — To  illustrate  how  folding  and  denudation 

bring  to  light  valuable  mineral  deposits.     The 

black  layer  may  represent  a  bed  of  coal.     If  tlie 

strata  were  horizontal,  it  might  be  deeply  buried  ; 

but  folding  has  raised  it,  and  deep   mountain 

valleys  have  exposed  it  to  the  air. 

valleys  in  the  moun- 
tain rocks  (Fig.  191).  Sometimes  they  are  preserved  from  erosion 
by  being  folded  down  in  the  synclines,  as  in  the  case  of  the  anthra- 
cite coal  of  Pennsylvania  (Fig.  194).  This  was  formed  at  the 
eame  time  as  the  bituminous  coal  that  is  found  west  of  the  Appa- 
lachians ;  but,  during  the  folding  of  these  mountains,  the  pressure 


H      L 


Scale  of  Miles 
2  a 


BOBJIW  4  CO.,   Njr.     , 


Contour  Interval  3'i}4  feet. 


Fig.  192.  — Topographic  map  of  Appalachian  ridges  where  crossed  by  the  Sus- 
quehanna above  Harrisburg,  showing  the  broad  valleys  and  the  narrow, 
Bteep-sided  water  gaps.  See  Figs.  172  and  173.  ^Harrisburg  Sheet,  U.  S. 
Bteoloffical  Survey  Topographic  Map-'i 


MOUNTAINS, 


109 


metamorphosed  it  to  "  hard  "  or  anthracite  coal.  At  Scranton, 
Wilkes  Barre,  and  elsewhere,  the  anthracite  is  now  being  removed 
from  the  synclines  in  which  it  has  been  so  long  preserved. 


BQRMAY    &    CO.,    N.Y 


Fig.  194.  —  A  section  of  the  coal  beds  (dark  layers)  at  Wilkes  Barre.    They  have 
been  folded  down  in  a  syncline,  and  thus  preserved  from  erosion. 

Summary.  —  Many  mountains  contain  valuable  mineral  dejmsits^ 
which  attract  settlers.  Folding  and  erosion  help  to  reveal  these 
deposits  ;  and  soynetimes  they  are  preserved  in  the  synclines. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  —  64.  Introductory.  —  Influence  of  momitains  on 
settlement;  reasons  for  studying  about  mountains. 

65.  The  Mountain  Rocks.  —  Position  of  rocks ;  faulting ;  folding ;  com- 
plex folding ;  Appalachians ;  kinds  of  rock ;  effect  of  complexity. 

66.  Names  applied  to  Parts  of  Mountains.  —  System ;  range  ;  cordillera ; 
ridge  ;  peak  ;  interior  basin ;  smaller  basins  ;  park ;  water  gap ;  pass. 

67.  Climate  of  Mountains.  —  (a)  Temperature  :  normal  change ;  snow 
line;  timber  line;  variation.     (6)  Rainfall:  rainy  slopes;  arid  slopes. 

68.  Denudation  of  Mountains.  —  (a)  Kiver  erosion,  (h)  Weathering  : 
reasons  for  activity,  (c)  Talus  :  cause ;  form  produced ;  change  to  farm 
land ;  debris  cones,  (d)  Avalanches  :  size ;  effects ;  Simplon  avalanche ; 
cause,     (e)  Effect  of  denudation  on  land  form. 

69.  Resemblance  between  Mountains  and  High  Plateaus.  —  Resemblance 
in  height;  in  ruggedness ;  the  Catskills;  difference  from  mountains. 

70.  Distribution  of  Mountains.  —  In  open  ocean  ;  fringing  continents,  — 
as  islands,  peninsulas,  and  continent  borders;  in  interior;  direction. 

71.  Cause  of  Mountains.  —  Contraction  theory ;  successive  uplifts  ;  slow 
growth;  absence  of  mountains  in  certain  sections. 

72.  Types  of  Mountains.  —  Faulted  blocks ;  domes ;  regular  folds ; 
complex  folds;  cause,  characteristics,  and  examples  of  each. 

73.  Life  History  of  Mountains. —  (a)  Young  mountains  :  early  growth  ; 
earthquakes;  volcanoes;  increasing  denudation;  valleys;  unfitness  for 
occupation;  examples.  (&)  Mature  mountains:  broadening;  lowering; 
examples ;  fitness  for  occupation,     (c)  Old  mountains :  further  reduc- 


110  NEW  PHYSICAL   GEOGRAPHY. 

tion ;   peneplain;  settlement;    instance;    Piedmont  belt,     (d)  Renewed 
elevation  :  Appalachians  ;  ridges ;  broad  valleys ;  settlement ;  water  gaps. 

74.  The  Drainage  of  Mountains.  —  («)  Consequent  drainage :  stream 
courses;  lakes.  (6)  Life  history  —  compare  with  plains,  (c)  Mono- 
clinal  shifting :  nature  of  process ;  law.  (cQ  River  pirates :  battle  at 
headwaters;  favoring  conditions ;  Catskills;   Appalachians;  wind  gaps. 

75.  Settlement  of  Mountains.  —  (a)  Unfavorable  conditions,  (b)  The 
Alps:  the  base;  the  slopes;  above  the  timber  line;  above  the  snow  line. 

76.  Mountains  as  Barriers.  —  Reasons ;  instances ;  overcoming  bar- 
riers, —  roads,  railways,  tunnels. 

77.  Mountains  as  Summer  Resorts.  —  Attraction  ;  mountains  visited  in 
eastern  United  States  ;  the  Alps  ;  importance  to  Switzerland. 

78.  Mountains  as  Timber  Reserves.  —  Reasons  for  forests ;  instances. 

79.  Mineral  Wealth  of  Mountains.  —  Alps;  the  West;  the  East;  effect 
on. settlement;  effect  of  folding  and  erosion ;  anthracite  coal. 

Questions.  —  64.    Of  what  importance  are  mountains  to  men  ? 

65.  What  is  the  position  of  the  mountain  rocks?  What  differences 
are  there  in  the  folds  ?    In  the  rocks  ?    What  effect  has  this  complexity  ? 

66.  What  are  the  following,  and  what  causes  each :  mountain  system, 
range,  cordillera,  ridge,  peak,  interior  basin,  park,  water  gap,  and  pass  ? 

67.  What  is  the  snow  line?  The  timber  line?  How  do  they  vary? 
What  effects  have  mountains  on  rainfall? 

68.  Why  are  rivers  and  weathering  very  active  in  mountains?  What 
becomes  of  the  fragments  that  fall?  What  are  the  nature,  effects,  and 
causes  of  avalanches  ?     What  effect  has  denudation  on  mountains  ? 

69.  Compare  and  contrast  high  plateaus  and  mountains. 

70.  In  what  situations  are  mountains  found?  Give  illustrations. 
What  about  the  direction  of  mountain  ranges? 

71.  State  the  theory  of  contraction.     How  do  mountains  grow? 

72.  Give  four  types  of  mountains.  AVhat  are  the  characteristics  of 
each?     How  do  they  differ?     Are  they  alike  in  any  respect? 

73.  What  happens  when  a  mountain  is  rising?  What  effect  has 
denudation?  What  are  the  characteristics  of  young  mountains?  Trace 
the  development  through  maturity  to  old  age.  Give  illustrations  of  each. 
What  is  a  peneplain  ?  What  has  been  the  history  of  the  Piedmont  Belt? 
What  changes  have  occurred  in  the  Appalachians  ? 

74.  Describe  the  consequent  drainage  of  mountains.  What  is  the 
normal  life  history?  What  causes  lakes?  How  does  the  law  of  mono- 
clinal  shifting  operate ?  What  are  river  pirates  ?  Why  do  they  succeed? 
Give  illustrations.     Explain  wind  gaps  (Fig.  178). 

75.  Why  are  mountains  sparsely  settled?  How  does  the  appearance 
of  the  Alps  change  from  base  to  summit?     How  do  the  occupations  vary  ? 


MOUNTAINS,  111 

76.  Why  are  mountains  barriers  to  the  spread  of  animals  and  plants? 
Give  illustrations.     How  are  these  barriers  now  overcome  by  men  ? 

77.  What  attracts  people  to  mountains?     Give  instances. 

78.  Why  is  there  much  forest  among  mountains?     Give  illustrations. 

79.  What  mineral  deposits  are  found  among  mountains?     What  effect 
have  mountains  in  revealing  and  protecting  mineral  deposits? 

Suggestions.  —  (1)  Slowly  dry  an  apple.  Notice  how  the  skin  wrin- 
kles as  the  inside  grows  smaller  through  the  evaporation  of  the  water. 
Compare  this  with  what  is  happening  in  the  earth.  (2)  Find  out  how 
the  tire  of  a  wagon  wheel  is  put  on,  and  why  it  fits  so  tight.  (3)  Get 
a  metal  rod,  and  have  a  thick  metal  ring  made  just  too  small  to  fit  over 
it.  Heat  the  ring  red-hot  and  see  if  it  goes  over  the  rod.  Have  another 
ring  made  to  fit  the  rod  exactly.  Heat  the  rod  and  see  if  the  ring  will 
go  over  it.  What  does  this  show  ?  (4)  See  suggestion  for  covering  a  ball, 
given  on  page  99.  (5)  It  is  not  very  difficult  to  make  an  apparatus  for 
imitating  the  folding  of  rocks.  Of  one-inch  boards  make  a  long,  narrow 
box,  say  2  feet  long,  5  inches  wide,  and  8  inches  deep,  open  at  one  end 
and  the  top.  Place  four  or  five  thin  layers  of  wax,  differently  colored, 
on  the  bottom.  At  the  open  end  apply  slow,  steady  pressure,  best  obtained 
by  using  a  screw,  like  that  which  sets  a  vise,  fastened  to  a  board  that  just 
fits  into  the  end  of  the  box.  Before  applying  the  pressure,  place  over  the 
wax  layers  enough  of  shot  to  nearly  fill  the  box.  After  pushing  the  layers  a 
few  inches,  remove  the  shot,  unscrew  one  side,  and  the  layers  will  show  fold- 
ing. A  simpler  experiment  may  be  made  by  taking  a  series  of  pieces  of 
thick  cloth  and  felt,  cutting  them  to  the  same  size,  and  pressing  them  up 
with  the  hand.  (6)  Is  your  home  among  mountains,  or  have  you  ever 
been  among  mountains?  What  is  the  nature  and  position  of  the  rocks? 
Do  the  mountains  rise  above  the  timber  line?  Are  they  young,  mature, 
or  old  ?  Are  they  well  settled  ?  Why  ?  Are  there  forests  ?  Mineral  ? 
Are  they  resorted  to  in  summer?     Why? 

Reference  Books.  —  King,  Mountaineering  in  the  Sierra  Nevaday 
Scribner's  Sons,  New  York,  1902,  ^1.50 ;  Lubbock,  Scenery  of  Stcitzerlajidy 
Macmillan  Co.,  New  York,  1896,  |1.50;  Russell,  Southern  Oregon,  4th 
Annual  U.  S.  Geological  Survey,  p.  435 ;  Tarr,  Physical  Geography  of 
Neio  York  ^Sfa/e,  Chapter  III,  Macmillan  Co.,  New  York,  1902,  $3.50; 
Hayes,  Physiography  of  the  Chattanooga  District,  Part  II,  19th  Annual 
U.  S.  Geological  Survey,  p.  9;  Willis,  The  Northern'  Appalachians, 
National  Geographic  Monographs,  American  Book  Co.,  New  York,  1895, 
$2.50;  Hayes,  The  Southern  Appalachians,  same;  Willis,  Mechanics 
of  Appalachian  Structure,  Part  II,  13th  Annual  U.  S.  Geological  Survey, 
p.  217. 


CHAPTER  VII. 

VOLCANOES,  EARTHQUAKES,  AND  GEYSERS. 

VOLCANOES. 

80.  Graham  Island.  —  South  of  Sicily,  in  1831,  a  new  vol- 
cano was  born.  During  the  eruption  large  volumes  of  steam 
rose  into  the  air,  carrying  up  fragments  of  lava.  The 
expansion  of  the  steam  in  the  melted  rock  caused  numerous 
cavities,  and  broke  the  lava  into  bits  of  porous  ash  and 
pumice.  Some  of  the  lightest  ash  drifted  away  in  the  wind  ; 
much  of  the  pumice  was  light  enough  to  float  on  the  water ; 
but  many  of  the  heavier  fragments  fell  back  near  the  outlet, 
building  a  cone  which  rose  200  feet  above  the  sea  and  had 
a  circumference  of  almost  three  miles.  With  this  single 
eruption  the  life  of  the  volcano  seems  to  have  ended ;  and 
soon  the  waves  cut  the  loose  ash  cone  away,  leaving  a  shoal  ' 
to  mark  its  site. 

Other  volcanoes,  some  in  the  sea,  some  on  the  land,  have 
become  extinct  after  a  single  gasp ;  but  most  volcanoes 
have  a  longer  and  more  varied  life.  From  some,  ash  is 
always  erupted ;  from  others,  streams  of  liquid  lava ;  and 
from  many,  now  ash,  now  lava.  Some  erupt  freely  and  at 
frequent  intervals ;  others  have  violent  outbreaks,  following 
long  periods  of  quiet.  These  differences  between  volcanoes 
may  best  be"  illustrated  by  studying  a  few  typical  ones. 

Summary.  —  Graham  Island  became  extinct  after  a  single  enqMon 
of  ash  and  immice,  formed  by  the  bloiving  up  of  melted  rock  by  in^ 
duded  steam.     Other  volcanoes  have  a  much  more  varied  history, 

112 


VOLCANOES,  EARTHQUAKES,  AND  GEYSERS,        113 


81.  Stromboli.  —  Between  Sicily  and  Vesuvius,  in  the  Lipari 
Islands,  is  the  ever  active  volcano  Stromboli.  It  is  a  small  cone, 
about  6000  feet  from  bottom  to  top,  half  its  height  being  above 
sea  level.  Steam  rises  from  a  crater  on  one  side  of  the  cone, 
and  the  steam  clouds  glow  with  light  from  the  melted  lava, 
which  always  stands  in  the  crater.  Every  few  minutes  the 
steam  erupts  masses  of  lava;  and  sometimes  there  is  a  mild  erup- 
tion which  throws 
pieces  outside  the 
crater.  The  cone 
is  made  of  such 
fragments. 


Summary.  — 

Stromboli  is  a  vol- 
cano made  of  frag- 
ments of  lava  thi'oivn 
out  by  mild  erup- 
tions. 

82.  Eruptions 
of  1902  in  the 
West  Indies.  — 
On    the    8th    of 


Fig.   195.  —  Vulcano,  oue  of  the  Lipari  Isiauds,  in  full 
eruption.    This  cone  is  now  inactive. 

May,    1902,    the 

beautiful  city  of  St.  Pierre,  in  Martinique,  was  wiped  out 
of  existence  by  a  terrible  volcanic  eruption  from  Mont  Pel6 
(Fig.  197).  Between  25,000  and  30,000  people  were  killed 
in  a  few  seconds,  and  only  one  person  in  St.  Pierre,  a 
prisoner  in  the  jail,  escaped  death.  On  the  previous  day 
there  was  a  destructive  eruption  from  the  volcano  of  La 
Soufriere,  in  the  neighboring  island  of  St.  Vincent. 

The  last  previous  eruption  of  Mont  Pele  was  in  1851  ;  in 
1812  there  was  a  terrific  and  destructive  eruption  of  La 
Soufriere.  The  people  of  St.  Pierre  had  almost  forgotten 
that  danger  lurked  in  the  slumbering  volcano ;  and,  though 
the  outbreak  of  1902  was  preceded  by  distinct  warnings, 


114 


NEW  PHYSICAL   GEOGRAPHY, 


Macouba 


Cape  St. Martin' 


few  heeded  them.  On  April  25  warm  water  was  re- 
ported in  the  old  crater  ;  later,  dust-laden  steam  rose  from 
it ;  then  a  lake  rose,  overflowing  the  crater  rim  on  May 
5,  and  sending  a  deluge  of  hot  water  and  mud  down  a 
valley. 

On  the  8th  of  May  came  the  eruption.     A  huge  column  of 
steam,   expelled   with  great  force,   bore  heated   sulphurous 

gases,  dust,  ashes, 
and  stones  high 
in  the  air.  The 
eruption  was  not 
nearly  so  violent 
as  many  other 
eruptions ;  but, 
owing  to  the  fol- 
lowing peculiar 
condition,  its  ef- 
fect was  very  dis~ 
astrous.  On  the 
side  toward  St. 
Pierre  there  was 
a  break  in  the 
crater  wall,  with 
a  valley  leading 
toward  the  city. 
Down  this  valley 
some  of  the  steam, 
with  its  l()i:d  of 
hot  rock  frao^- 
ments  and  gases, 
rushed  with  the  violence  of  a  tornado,  destroying  everything 
in  its  path.  It  overturned  trees  and  lionses,  and  even  car- 
ried a  hollow  iron  statue,  11  feet  high,  a  distance  of  50  feet. 
Most  of  the  deaths  were  probably  caused  by  breathing  the 
steam  and  hot  ashes. 


ENGLISH   M.LES 


BcnMAr  *  CO.,  N.v. 


0  i  i>  3  4  5 

Fig.  1%.  —  The  vicinity  of  Mont  Pele.     The  shaderl 
area  shows  the  zone  of  destruction. 


Fig.  197.  —  The  ruins  of  St.  Pierre,  from  a  photograph  taken  June  14.     Mont 

Pele  is  in  the  background. 


Btfy''iii,|fj.ijji^yyLM-i.iuiiiiiyii<yiiiii|ij>^ijniMi^^^^^^^ 


l>-'- 


<  •?•—'■ 


nit  i;-i«iiri'iHii\i  iniiiirfitrilflli'  ViT' 


Fig.  198.  — Valley  of  the  Roxelane,  near  be.  Pierre,  as  ic  appeared  May  22, 1902, 
—  the  trees  killed  and  the  surface  covered  with  volcanic  ash.        p  114a 

(From  puotographj  io<»>ed  by  E,  O   Hovey  of  the  American  Museuro  of  Natural  Hist ^r'-  ) 


Fig.  199. — Vesuvius  from  Poujpeii,  whose  ruius  are  now  largely  excaviu 
The  remnant  of  Monte  Somma  forms  the  ridge  on  the  right,  while  the  pre 
ent  cone  of  Vesuvius  rises  in  the  middle. 


still  be  plainly  seen.    Ash  completely  covered  all  the  buildiard  and  filed 
every  crevice  compaewy-    Parts  of  the  city  are  not  yet  uncove?p<i. 


VOLCANOES,   EARTHQUAKES,   AND   GEYSERS,        115 


There  have  been  several  later  outbursts,  all,  like  the  first, 
erupting  ash,  with  no  flowing  lava  and  with  no  destructive  earth- 
quake shocks.  The  eruptions  have  built  a  cone  1500  to  2000  feet 
high  in  the  old  crater,  and  the  ash  has  fallen  over  the  whole 
island  (Fig.  198)  and  the  sea  round  about.  After  the  eruption  of 
June  6,  a  quarter  of  an  inch  of  ash  fell  upon  a  ship  over  100 
miles  from  the  volcano.  At  a  distance  from  the  volcano  the  ash 
deposit  is  thin ;  but  on  and  near  the  cone  it  is  several  feet  deep, 
resembling  freshly  fallen  snow.  During  each  eruption  the  con- 
densed steam  causes  heavy  rains,  which  wash  vast  quantities  of 
loose  ash  down  the  steep  slopes  in  destructive  mud  flows.  Some- 
time —  no  one  can  foretell  when  —  the  eruptions  will  cease,  prob- 
ably to  break  out  again  when  energy  enough  has  accumulated. 

Summary.  —  In  May,  1902,  after  a  long  period  of  quiet,  Mont 
Pele  and  La  Soufrih^e  hurst  forth  in  eruptions  of  ash,  causing  much 
destruction.  There  have  been  numerous  eruptions  since  then,  and 
vast  quantities  of  volcanic  ash  have  been  thrown  out  upon  the  islands 
and  the  sea  round  about.  The  condensed  steam,  forming  rain,  has 
ivashed  much  ash  down  the  volcano  side,  coMsing  mud  flows. 

83.  Vesuvius.  —  At  the  beginning  of  the  Christian  era,  Ve- 
suvius, like  Pele,  had  long  been  inactive,  and  people  had  no 
fear  of  it.  It  had 
been  quiet,  or  dor- 
mant, for  centuries, 
and  was  not  even 
recognized  as  a  vol- 
cano. Farms  and 
villages  dotted  the 
slopes  of  Monte 
Somma  (Fig.  201), 
as  it  was  called, 
and     cities      were 

located  at  its  base.  In  the  year  79  it  broke  forth  in  a  ter- 
rible eruption  which  buried  the  farms  and  villages  beneath 
ash,  and  destroyed  Pompeii  and  Herculaneum, 


Fig.  201.  —  The  form  of  Vesuvius,  or  Monte  Somma, 
before  79,  according  to  Strabo.  Only  a  part  of 
the  crater  rim  now  stands  (Fig.  199),  the  present 
cone  rising  on  the  site  of  that  part  of  the  crater 
nearest  us. 


ti6 


NEW  PRYSICAL  GEOGRAPHY, 


Before  the  eruption  there  were  frequent  earthquakes,  one  v^r 
which  partly  destroyed  Pompeii ;  and,  finally,  a  terrific  explosion 
occurred  by  which  half  the  crater  wall  was  blown  away.  The 
ashes  rose  thousands  of  feet  in  the  air,  settling  on  all  the  country 
round  about.  The  naturalist  Pliny,  admiral  of  the  Eoman  fleet, 
who  was  at  Misenum  (near  C.  Miseno,  Fig.  202),  started  toward 
the  mountain  and  lost  his  life.  Letters  of  Pliny's  nephew  to  the 
historian  Tacitus,  telling  of  the  death  of  his  uncle,  are  the  only 
description  of  the  eruption  that  we  have. 


SALERNO 


Fig.  202.  —  Map  of  the  Bay  of  Naples.    There  are  numerous  volcanic  cones  from 

Pozzuoli  to  Ischia. 


The  day  was  changed  to  the  darkness  of  night  by  a  heavy  cloud 
of  ash ;  hot  ashes  and  stones  fell  all  about ;  the  air  was  filled  with 
sulphurous  gases ;  the  ground  was  violently  shaken ;  there  was 
fierce  thunder  and  lightning;  and  the  cries  of  terror  from  the 
people,  who  rushed  madly  about,  added  to  the  din.  Thousands  of 
people  were  undoubtedly  killed,  though  there  is  no  record  of  the 
number,  nor  even  of  the  villages  destroyed. 

Pompeii  and  Herculaneum  have  been  discovered  and  partly 


Fig.  203.  —  Vesuvius  in  eruption  in  1872,  sliowing  the  steam  rising  from  tlie 
crater;  also  from  ttie  lava  that  is  flowing  down  the  slopes 


FiQ.  204. -The  ordinary  condition  of  Vesuvius.     The  lava  in  the  fore^rouTi^ 

was  erupted  in  1858  «  ioreground 


Fig.  205  —  The  cone  of  Vesuvius,  in  moderate  eruption,  July  5,  1895 


Fro.  206. —  A  view  into  the  crater  ol  Vesuvius.  This  photograph  was  taken 
during  the  above  eruption,  when  the  lava  was  drawn  out  of  the  crater.  At 
ordinary  times  tb**  crater  is  se  illed  with  steam  that  one  cannot  look  f»r 
dawn  into  it 


jipj|p«i«Meafipiiipii;iff«liijp^ 


TfTTlW^TTr*^ 


mnw"  >»i.«wprsipen 


iriG.  207.  —  Monte  Xuovo,  a  small  ash  cone,  at  the  head  of  the  Gulf  of  Pozzuoli 
(Fig.  202),  which  was  thrown  up  during  an  eruption  in  1538.  It  has  not 
erupted  since,  B,nd  its  slojies  are  now  cultivated. 


Fig.  208.  —  The  crater  of  another  volcano  at  Pozzuoli,  aJso  extinct.  Steam  and 
sulphurous  gases,  forming  sulphur  crystals,  still  rise  in  this  crater,  and 
vegetation  is  unable  to  grow  where  tb^y  lise. 


Fig.  209.  —  Etna,  with  steara  rising  from  its  crater.     Several  small  cones,  built 
during  eruptions,  are  also  shown  on  the  flanks. 


FiQ.  210.  — An  eruption  on  the  flanks  oi  i>tiia,  showing  steam  rising  from  one 
of  the  small  cones-    Tue  distant,  snow-covered  peak  is  Etna. 


VOLCANOES,   EARTHQUAKES,   AND  GEYSERS,        117 

excavated  (Fig.  199).  From  these  excavations  we  learn  what  the 
life  of  the  Romans  was  on  the  day  of  that  fearful  outbreak  nearly 
1900  years  ago.  The  houses  had  been  so  well  preserved  beneath 
che  ash  that  even  pictures  painted  on  the  walls  are  still  quite  per- 
fect. It  is  a  wonderful  experience  to  walk  through  those  deserted 
streets  (Fig.  200),  and  to  see  how  the  people  lived,  and  what  they 
did,  as  if  they  had  left  but  yesterday.  Yet  it  is  a  picture  of  life 
almost  at  the  time  of  Christ. 

Since  79  Vesuvius  has  had  many  eruptions,  some  violent, 
some  moderate  (Fig.  205),  some  of  ash,  some  of  lava  (Fig. 
203).  The  remnant  of  old  Monte  Somma  still  stands  on  one 
side  of  the  present  cone,  which  rises  4200  feet  above  the  level 
of  the  Bay  of  Naples  (Fig.  202).  At  most  times  visitors  may 
go  to  the  YQTj  edge  of  the  crater  (Fig.  206).  Standing  on 
the  side  from  which  the  wind  blows,  one  looks  down  into  a 
deep  hole,  out  of  which  vast  quantities  of  steam  rise  with  a 
roar,  bearing  sulphurous  gases.  Every  few  seconds  there  is 
a  slight  explosion,  when  masses  of  red-hot  lava  are  thrown 
up,  often  higher  than  the  crater  wall.  At  night  the  lava 
in  the  crater  causes  a  glow  on  the  cloud  that  overhangs 
Vesuvius. 

Occasionally  the  volcano  grows  more  active  ;  then  hot 
stones  rise  so  high  that  they  fall  on  the  crater  edge,  and  it  is 
unsafe  to  stand  there.  This  may  increase  until  the  stones 
fall  some  distance  beyond  the  crater.  The  small  cinder  cone 
that  surrounds  the  crater  is  made  of  these  loose  fragments. 

Now  and  then  lava  issues  from  the  cone,  flowing  in  a  great 
stream,  sometimes  clear  to  the  sea.  The  recent  flows  form 
great  black,  rugged  scars  on  the  volcano  side  (Fig.  204); 
the  older  ones  are  partly  decayed  and  covered  v/ith  a  soil. 
There  is  an  observatory  on  the  slope  of  Vesuvius  in  which 
scientists  study  the  volcano  and  attempt  to  predict  eruptions, 

Vesuvius  is  only  one  of  several  volcanic  cones  in  the  Bay  of 
Naples  (Figs.  207,  208).  The  famous  lake  Avernus  is  in  a  vol- 
canic crater ;  the  island  of  Ischia  is  a  volcano  (Fig.  202) ;  and 


118  NEW  PHYSICAL   GEOGRAPHY, 

there  are  several  others  in  the  same  region.  All  of  them  have 
been  long  extinct,  though  hot  water,  steam,  and  gases  still  rise 
in  some  places.  There  are  numerous  proofs  that  changes  in 
level  of  the  land  have  accompanied  the  volcanic  activity  of  this 
region  (Fig.  37). 

Summary.  —  In  the  year  I'd,  after  being  long  dormant,  Vesuvius 
hroJce  forth  in  violent  eruption,  jyttrtially  destroying  the  cone  and 
burying  Pompeii  and  Herculaneuni,  lohich  have  been  ivell  preserved 
beneath  the  volcanic  deposits.  Since  then  Vesuvius  has  had  many 
eruptions  of  ash  and  lava,  some  of  them  very  violent.  Ordinarily 
it  is  so  quiet  that  one  may  go  to  the  very  edge  of  the  crater,  from 
ivhich  steam  constantly  rises,  bearing  upward  masses  of  lava.  In 
the  neighborhood  there  are  extinct  volcanoes. 

84.  Etna.  —  The  greatest  volcano  in  the  Mediterranean  is 
Etna,  on  the  eastern  end  of  Sicily.  Steam  rises  from  its 
crater  (Fig.  209),  and  every  few  years  there  is  an  eruption. 
Then  lava  issues  from  fissures  in  the  mountain  side  and  flowc 
in  enormous  masses  down  the  slopes,  even  to  the  sea,  often 
destroying  villages  on  the  way.  There  are  scores  of  small 
cones,  200  to  300  feet  high,  built  along  these  fissures  (Figs. 
209,  210). 

Etna  rises  10,870  feet  above  the  sea,  and  at  its  base  has  a  cir- 
cumference of  over  60  miles.  It  is  so  high  that,  although  oranges 
and  bananas  grow  at  its  base,  the  climate  at  the  top  is  frigid. 
This  great  cone  is  made  entirely  of  lava  and  ash  forced  out  from 
within  the  earth  by  steam.  The  recent  lava  flows,  those  only  a 
few  score  years  old,  are  barren  masses  of  black  rock  too  rough  to 
cross.  But  this  lava  decays  so  readily,  and  forms  so  fertile  a 
soil,  that  in  a  century,  portions  of  a  flow  are  fit  for  cultivation. 
Soil  is  often  gathered  in  baskets  and  placed  between  the  lava 
blocks  for  the  planting  of  grapevines. 

Summary. —  The  huge  cone  of  Etna  is  inade  of  lava,  issuing 
mainly  as  great  flows  from  fissures  in  its  flanks.  Tliis  lava  decays 
quickly,  forming  a  fertile  soil. 


VOLCANpES,   EARTHQUAKES,   AND   GEYSEJRS.       119 

85.  Krakatoa.  —  For  a  century  the  small  volcanic  island  of 
Krakatoa,  near  Java,  in  the  Straits  of  Sunda,  was  dormant. 
In  August,  1883,  it  broke  forth  in  the  most  terrific  erup- 
tion that  civilized  man  has  known.  A  large  part  of  the  cone, 
together  with  ash  from  below,  was  hurled  high  into  the  air, 
and  the  site  of  the  destroyed  cone  was  occupied  by  water  1000 
feet  deep  (Fig.  220).  Every  vestige  of  life  on  the  island  was 
destroyed,  and  its  surface  was  deeply  covered  with  ash. 

For  miles  around,  the  sea  was  so  thickly  covered  with  pumice 
that  the  movement  of  vessels  was  interfered  with.  The  finer  ash 
was  thrown  so  high  into  the  air  that  it  was  carried  all  round  the 
earth,  causing  brilliant  sunsets  in  Asia,  Europe,  and  America. 

So  violent  was  the  explosion  that  a  great  air  wave  was  started 
which  passed  three  times  around  the  earth.  Windows  were 
broken  100  miles  from  the  volcano,  and  the  sound  of  the  explo- 
sion was  heard  more  than  150  miles  away.  A  water  wave  was 
also  caused  which  spread  all  over  the  Pacific,  being  measured  on 
the  coasts  of  Africa,  Australia,  and  California.  Xear  the  volcano 
this  wave  washed  over  the  land  to  a  height  of  50  to  100  feet,  kill- 
ing 35,000  people. 

Since  then  Krakatoa  has  been  quiet.  It  may  have  become 
extinct;  but  more  probably  it  is  only  dormant,  and  will  again 
burst  forth  when  the  pent-up  steam  once  more  gathers  suffi- 
cient energy  to  force  its  way  to  the  surface. 

Summary.  —  After  a  century  of  quiet,  Krakatoa  burst  forth,  in 
1883,  in  the  most  violent  eruption  known.  Half  the  cone  ivas  bloivn 
away  ;  ash  fell  all  about,  and  was  carried  far  ayid  wide  by  the  ivinds; 
a  great  air  wave  passed  three  times  round  the  earth;  and  a  water 
luave  spread  over  the  Pacific.     Since  then  the  volcano  has  been  quiet. 

86.  Hawaiian  Volcanoes. — There  are  numerous  volcanic 
cones  in  the  Hawaiian  Islands  (Fig.  221),  most  of  them  ex- 
tinct. The  two  highest  are  Mauna  Loa  and  Mauna  Kea, 
which,  with  the  smaller  Kilauea,  are  on  the  island  of  Hawaii 
(Fig.  211).     This  island,  the  greatest  volcanic  mountain  in 


120 


NEW    PHYSICAL    GEOGRAPHY, 


^      West    155130'      from       Greenwich  155 


the  world,  nses  nearly  14,000  feet  above  isea  level,  and  30,000 

feet  above  the  sea  floor. 

On  the  top  of  Mauna  Loa  is  a  great  crater  two  or  three 

miles  in  diameter.     This  is  partly  frozen  over,  but  steam  rises 

from  cracks  in  the  surface,  and  in  one  part  there  is  a  lava 

lake,  from  which 
jets  or  fountains 
of  lava  rise,  some- 
times several  hun- 
dred  feet.  A 
similar  condition 
exists  in  the  crater 
of  Kilauea ;  but 
Mauna  Kea  is  ex- 
tinct. Such  ex- 
tensive craters 


p>A\'^aimanu 


Dokala 


(Figs.  212,  213) 
are  called  calderas. 
The  lava  slowly 
rises,  overflowing 
the  crater  floor 
and  freezing  on 
it  (Fig.  212),  as 
water  sometimes 
flows  over  the  ice 
on  a  pond.  Be- 
fore the  lava  rises 
high  enough  to  flow  out  over  the  rim  of  the  crater,  its  weight 
and  the  steam  pressure  usually  open  a  fissure  in  the  moun- 
tain side  through  which  the  lava  is  drained  (Fig.  211). 
This  occurs,  on  the  average,  once  in  about  seven  years, 
and  no  violent  ash  eruptions  have  ever  been  recorded. 
The  fissures  are  usually  formed  above  sea  level,  but  some- 
times occur  beneath  the  sea.  Some  of  the  lava  streams  are 
30  or  40  miles  long  and  2  or  3  miles  wide. 


Fig.  211.— The  dark  areas  represent  lava  flows  which 
start  from  fissures. 


Fig.  212.  —  Lava  lake,  frozen  at  the  surface,  iu  the  crater  of  a  Hawaiian  volcano. 


Fig.  213. — Lava  lake  in  the  crater  of  a  Hawaiian  volcano. 


Afa^ikw_Ml*A«ili«di«^M_«»^_ 


»^^'S^ 


ti\j,.  214.  —  .Ml.  biiasta,  California.  On  the  right  is  Shastina,  a  newer  cone  on  the 
flanks  of  the  main  volcano.  Both  these  cones  are  extinct ;  but  Shastina  still 
has  a  crater,  while  the  crater  of  Shasta  has  been  destroyed  by  denudation. 


Fig.  215.  —  Crater  Lake,  Oregon,  the  deepest  lake  in  North  America.  The  little 
island,  called  Wizard  Island,  is  a  cone  built  up  from  the  bottom  of  the  crater 
tiuce  it  collapsed.  _ 


SECTION   FROM  A  TO  B 


IBOBHAr    i    Cl)^,    N.Y. 


Fig.  216.  —  Topographic  map  of  Crater  Lake.  Notice  the  other  smaller  craters 
and  cones  near  by.  A  section  through  the  mountain,  along  the  line  AB,  is 
shown  at  the  bottom,  (Crater  Lake  Special  Sheet,  U.  S.  Geological  Survey 
'^oographic  Map.) 


^^■R^^^^^ 

iiiif^ffffi 

r 

Fig.  217.  — Flowing  lava  in  Hawaii,  1881. 


Fig    218  —  Lava  cascade,  similar  to  the  above,  with  the  lava  c/iled. 


VOLCANOES,   EARTHQUAKES,  AND  GEYSEBS.        121 

An  earthquake  shock  accompanies  the  opening  of  the  fissure, 
and  huge  volumes  of  steam  rise  from  the  glowing  lava  that  rushes 
forth.  At  first  the  lava  flows  rapidly  down  the  mountain  side ; 
but  it  soon  cools  and  solidifies  at  the  surface  (Figs.  217,  218). 
Then  the  movement  becomes  much  slower.  The  frozen  crust  is 
broken  and  rolled  along  by  the  movement  of  the  lava  beneath, 
and  liquid  lava  may  burst  through  the  solid  front  at  any  point. 
The  lava  front  advances  for  weeks,  always  more  and  more  slowly, 
and  years  may  pass  before  it  entirely  cools. 

Summary.  —  Hawaii,  the  greatest  volcanic  mountain  in  the  world, 
has  two  active  volcanoes  with  huge  craters,  or  calderas.  In  these  are 
lava  lakes  ivhich  steadily  rise,  once  in  about  seven  years  being  drained 
through  fissures  in  the  mountain  sides.  The  lava  at  first  fiows  rap- 
idly;  but,  as  it  cools  on  the  surface,  its  rate  offiow  is  checked. 

87.  Mt.  Shasta  and  Lassen  Peak.  — This  extinct  volcano 
(Fig.  214),  whose  elevation  is  over  14,000  feet,  resembles 
Etna  in  form.  From  its  snow-covered  top  small  glaciers 
descend  into  the  higher  valleys,  and  on  its  flanks  is  a  later 
cone. 

South  of  Shasta  is  the  extinct  cone  of  Lassen  Peak,  and  near 
its  base  an  ash  cone  about  650  feet  high  (Fig.  235).  The  size  of 
trees  that  have  grown  in  the  ash  indicates  that  it  was  erupted 
about  200  years  ago.  A  still  later  lava  eruption  has  dammed  a 
stream,  forming  Snag  Lake,  in  which  are  snags  of  trees  killed 
by  the  rise  of  the  water.  It  seems  probable  that  this  lava  flow  is 
not  much  ovor  a  century  old.  There  are  other  recent  lava  flows 
in  various  parts  of  the  West. 

Summary.  —  Shasta  is  a  lofty  extinct  volcano  ;  but  at  Lassen 
I'euk,  near  its  base,  there  have  been  7'ecent  eruptions  of  ash  and  lava. 

88.  Crater  Lake.  —  Another  extinct  volcano  in  western  United 
Statc-ii  '^si  occupied  by  Crater  Lake  in  Oregon.  This  lake,  which 
is  about  2000  feet  deep,  lies  in  a  huge  crater,  or  caldera  (Fig. 
216),  between  3000  and  4000  feet  in  depth,  and  about  6  miles  in 
diameter.  It  has  been  proved  that  a  lofty  volcano  (Fig.  219) 
rose  where  the  caldera  now  stands.     The  removal  of  lava  from 


122 


NEW  PHYSICAL   GEOGRAPBT- 


beneath  the  cone  allowed  it  to  collapse,  forming  the  caldera,  in 
which  a  later  eruption  has  built  a  small  ash  cone  (Fig.  215). 

Summary.  —  Cra- 
mer Lake  occupies  a 
huge  crater,  or  cal- 
dera, formed  by  the 
draining  off  of  lava 
from  beneath,  cauS' 
ing  the  cone  to  col- 
lapse. 


Fig.  219.  —  Section  of  Crater  Lake,  with  the  old  cone, 
named  Mt.  Mazama,  restored  by  the  dotted  line. 


89.  Materials  Erupted. — Every  volcanic  eruption  is  accom- 
panied by  vast  quantities  of  steam,  and  smaller  amounts  of 
sulphurous  and  other  gases.  These  gases  are  commonly 
called  "smoke,"  and  the  glow  of  light  reflected  from  the 
melted  lava  is  popularly  termed  "flame." 

If  the  eruption  is  moderate,  melted  rock  usually  flows  out, 
and,  in  cooling,  forms  lava  flows  (Figs.  217,  218).  Expan- 
sion of  steam  in  the  pasty  lava  makes  many  small  rounded 
cavities,  especially  near  the  top ;  and  the  surface  is  broken 
by  the  movement  of  the  lava  after  a  crust  has  been  formed. 
In  violent  eruptions  the  expansion  of  the  steam  blows  the 
lava  to  pieces,  forming  scoria^  pumice^  and  ash.  These  are 
so  light  and  porous  that  they  float  in  water,  and  the  fine 
ash  even  remains  suspended  in  the  air. 

Lumps  of  lava  thrown  into  the  air,  cooling  in  oval,  twisted 
masses,  are  known  as  volcanic  bombs  (Fig  236).  They  vary  from 
a  few  inches  to  many  feet  in  diameter.  During  eruptions  ilie 
condensation  of  the  steam  causes  heavy  rains,  accompanied  by 
vivid  lightning.  The  rain  often  washes  down  much  loose  ash, 
forming  mudjtoics. 

Summary.  —  Steam  and  other  gases  accompany/  all  volcanic  enip- 
tions.  Lava  comes  from  moderate  eruptions  ;  ash,  pumice,  and 
scoria  from  violent  ones.  Volcanic  bombs  are  also  thrown  out;  and 
rains  wash  down  the  ash,  forming  mudjloivs. 


VOLCANOES,   EABTHQUAKES,  AND   GEYSERS.        123 

90.  The  Forms  of  Volcanic  Cones.  —  A  volcano  is  a  conical 
peak  with  a  crater  at  the  top.  If  the  eruptions  are  of  ash  the 
cone  is  steep,  because  the  fragments  that  fall  back  near  the 
vent  have  aslope  as  steep  as  loose  ash  will  stand  (Fig.  221). 
On  the  other  hand,  cones  made  of  flowing  lava  are  broad  and 
have  a  low  slope  (Fig.  221).     (Compare  Figs.  223  and  224.) 

One  reason  for  these  differences  is  that  lava  flows  away  as 
a  liquid  ;  another,  that  some  of  it  starts,  not  from  the  top, 
but  from  fissures  on  the  slopes  of  the  cone  (Figs.  210,  211)  ; 
and  a  third  that  it  all  remains  on  the  cone,  while  in  ash 
volcanoes  a  large  part  is  drifted  away  by  the  winds.  When 
the  material  is  now  ash,  now  lava,  as  in  Vesuvius,  the  cone 
has  a  slope  intermediate  between  that  of  lava  and  ash. 

The  crater  of  a  volcano  may  be  so  large,  perhaps  from  one  to 
five  miles  in  diameter,  as  to  deserve  the  name  caldera.  In  addi- 
tion to  the  calderas  of  the  Hawaiian  Islands  (p.  120)  and  Crater 
Lake  (p.  121),  there  are  calderas  in  Italy,  the  Eifel  district  of 
Germany  (Fig.  225),  and  other  places.  The  craters  on  the  moon 
(Fig.  14)  are  enormous  calderas.  Calderas  may  be  caused  either 
by  collapse  of  the  cone,  or  by  violent  explosions  Avhich  blow  the 
top  of  the  cone  away.  In  some  cases,  as  in  Krakatoa  (Fig.  220), 
explosions  wreck  the  cone  and  make  it  irregular. 

Summary.  —  Ash  cones  have  a  steep  slope,  ivhile  lava  cones  are 
broader  and  more  gentle  in  slope.  Cones  consisting  of  both  ash  and 
lava  have  a  slope  between  the  tioo.  Calderas  are  huge  craters  caused 
either  by  the  collapse  or  by  the  bloiving  away  of  the  tops  of  cones. 

91.  Distribution  of  Volcanoes. — There  are  thousands  of 
volcanic  cones,  only  about  300  of  which  are  known  to  be  active. 
The  great  majority  of  these  cones  are  in  or  near  the  sea, 
far  the  greatest  number  being  in  the  mountains  and  islands 
which  partly  encircle  the  Pacific  Ocean  (Fig.  222). 

The  many  lofty  cones  in  the  Andes,  Central  America,  and 
southern  Mexico  are  in  this  belt.  Associated  with  it  is  the  vol- 
canic belt  of  the  Lesser  Antilles,  500  miles  long,  in  which  Mont 


124  NEW  PHYSICAL   GEOGRAPHY. 

Pele  and  La  Soufriere  are  situated.  Most  of  the  islands  of  the 
Lesser  Antilles  are  volcanic.  From  Mexico  northward,  through 
western  United  States,  are  hundreds  of  volcanic  cones,  all  either 
dormant  or  extinct.  Among  the  best  known  of  these  are  Mt. 
Ranier,  Mt.  Shasta,  Mt.  St.  Helens,  and  Mt.  Hood. 

The  Aleutian  Islands,  which  inclose  Bering  Sea,  form  a  volcanic 
chain  1600  miles  long,  including  57  volcanoes,  some  of  which  are 
very  vigorous.  From  Kamchatka  southward,  along  the  Kiirile, 
Japanese,  and  Philippine  islands,  there  is  another  great  chain  of 
volcanoes.  The  East  Indies  have  numerous  active  cones,  and  this 
chain  swings  down  to  New  Zealand. 

Practically  all  the  small  islands  of  J;he  open  Pacific  and  Indian 
oceans  are  volcanoes.  Even  the  coral  atolls  are  volcanic  cones 
with  a  veneer  of  coral. 

There  are  volcanic  areas  in  the  continents  of  Europe,  Asia,  and 
Africa,  including  a  line  extending  from  central  Africa  to  Asia 
Minor;  also  Mt.  Ararat;  volcanoes  in  the  Caucasus  Mountains; 
and  a  number  in  the  Mediterranean  near  Greece,  and  in  and  near 
Italy. 

The  islands  of  the  open  Atlantic  are  volcanic,  and  some  of 
them  are  active.  Iceland  has  a  number  of  volcanoes,  some  of 
which  have  had  terrific  eruptions.  The  Faroe  Islands  are  ancient 
volcanoes,  and  there  were  formerly  volcanoes  in  the  British  Isles. 
In  the  Azores  Islands,  which  are  all  volcanic,  there  are  hundreds 
of  cones  (Fig.  226),  some  of  which  were  in  eruption  during  the 
last  century.  The  Bermuda  islands  are  a  coral  group  on  a  vol- 
canic cone.  The  Cape  Verde,  Canary,  and  other  islands  farther 
south,  including  St.  Helena,  the  prison  home  of  Napoleon,  are  all 
volcanoes.  • 

In  spite  of  the  great  numbers  of  cones,  they  are  really  ex- 
ceptional land  forms.  By  far  the  greater  part  of  the  earth's 
surface  is  now  free  from  volcanic  action;  and  large  areas 
have  never  been  disturbed  by  eruptions.  In  other  places, 
as  in  eastern  United  States,  central  France  (Fig.  227),  and 
the  British  Isles,  volcanic  action  long  ago  died  out.  Both  at 
thp  present  time  and  in  the  past,  volcanic  activity  has  been 
associated  with  mountain  growth 


Fig.  220.  —  The  half  of  Krakatoa  left  after  the  eruption. 


—  Sea  teveX 


Fig.  221.  —  The  slopes  of  two  volcanoes,  one  ash  (dotted),  the  other  lava.  The 
latter,  represented  by  the  continuous  line,  may  be  considered  to  be  Mauna 
Loa.  Not  only  is  the  ash  cone  steeper,  but  it  contains  much  less  material, 
because  so  much  has  been  drifted  away  by  winds  and  ocean  currents.  See 
also  Figs.  223,  224. 


Fig.  222. — The  distribution  of  volcanoes.     The  shaded  sections  show  the  main 
areas,  and  the  dots  locate  some  of  the  active  or  recently  extinct  volcanoes. 


Fig.  223.  —  Chimborazo,  Ecuador,  20,500  feet  high;  so  high  that,  though  under 

the  equator,  it  is  snow-covered. 


WiQ.  224.  —  A  volcanic  lava  t;oje  m  uie  ii,<  v. .n-.i.i   i.-.i.iua»     Compare  its  low 
aiope  with  that  of  Chimborazo.    See  also  Fig.  221. 


I'lu.  SZ6.  —  A  volcanic  coue  in  the  Azores.     It  is  so  recent  that  it  has  a  perfect 
crater.    The  stone  walls  by  the  roadside  are  made  of  lava  blocks. 


Fig.  227. — Volcanic  peaks  in  the  Anver^ne  region,  a  volcanic  region  in 
central  France.  The  peaks  on  which  the  buildings  are  situated  are 
remnants,  or  necks,  of  volcanoes  partly  destroyed  by  denudation. 


VOLCANOES,    EARTHQUAKES,    AND    GEYSERS.         125 

Summary.  —  The  majoritu  of  volcanoes  are  in  or  near  the  sea, 
the  greatest  dclt  heing  in  the  chain  of  mountains  and  islands  ichich 
partly  encircle  the  Pacific.  There  are  many  volcanic  islands  in  the 
open  Pacific,  Indian,  and  Atlantic  oceans,  and  in  the  Mediterranean. 
Volcanoes  are  exceptional  land  forms.  They  have  never  been  present 
in  some  places  and  have  become  extinct  in.  others. 

92.  Cause  of  Volcanoes. — The  immediate  cause  for  a  vol- 
canic eruption  is  undoubtedl}^  the  explosive  force  of  pent-up 
steam.  It  is  believed  that  this  steam  is  caused  by  water  that 
percolates  clown  to  the  melted  rock.  As  it  slowly  accumu- 
lates, it  finally  gains  force  enough  to  push  its  Avay  to  the 
surface  and  carrv  some  of  the  melted  rock  with  it. 

It  is  probabk  that  the  folding  of  the  mountain  rocks 
squeezes  the  lava  upward  until  it  reaches  places  so  near  the 
surface  that  water  is  able  to  enter  it  and  force  it  the  rest  of 
the  way.  Faults  formed  during  mountain  growth  furnish 
pathways  for  the  rise  of  this  lava. 

When  mountains  stop  growing,  volcanic  activity  dies  out.  For 
this  reason  western  United  States,  which  in  the  last  geological 
period  was  a  region  of  intense  volcanic  activity,  is  now  almost,  if 
not  quite,  free  from  active  volcanoes.  There  may  yet  be  eruptions 
in  the  West ;  but  unless  there  is  a  renewal  of  mountain  growth, 
these  eruptions  will  probably  not  be  numerous. 

Summary.  —  Water,  descending  from  the  surface,  comes  in  contact 
with  melted  rock,  probably  squeezed  upward  during  mountain  folding . 
This  forms  steam  and  forces  the  lava  to  the  surface,  often  along 
faults.      When  mountain  growth  ceases,  volcanic  activity  dies  out. 

93.  Lava  Floods.  —  In  western  United  States,  in  addition 
to  volcanoes,  there  were  great  lava  floods  which  escaped  from 
fissures  and  deluged  the  surrounding  country.  They  were 
Perhaps  squeezed  out  as  a  result  of  mountain  growth,  some- 
what as  water  rises  through  a  crack  in  the  ice  of  a  frozen 
pond.  The  greatest  of  these  floods  was  in  the  valley  of  the 
Snako  and  Columbia  rivers  CFigr.  476).  mainly  in  Oregon, 


126  NEW  PHYSICAL   GEOGRAPHY. 

Idaho,  and  Washington,  where  an  area  of  fully  200,000  square 
miles  is  covered  with  lava.  By  these  lava  floods,  which  ex- 
tended up  Valleys  and  surrounded  mountains,  as  lake  water 
does,  an  irregular  land  surface  was  changed  to  a  great  lava 
plateau.  Deep  canyons  show  a  depth  of  3000  to  4000  feet 
of  lava,  layer  on  layer.  In  some  places,  as  in  the  Cascade 
Ranges,  blocks  of  this  lava  have  been  broken  and  tilted  to 
form  mountains. 

Throughout  the  Far  West  there  are  other  instances  of  lava 
floods,  for  example,  in  the  Yellowstone  Park.  Similar  floods 
have  been  formed  in  other  parts  of  the  world,  as  the  plateau 
of  the  Deccan  in  India,  which  in  extent  rivals  the  Columbia  lava 
plateau. 

At  present  such  lava  floods  are  nowhere  issuing  from  the 
earth.  The  nearest  approach  is  in  Iceland,  where  lava,  well- 
ing from  fissures,  has  built  a  broad  plateau.  When  such  a 
fissure  is  partly  closed,  leaving  only  one  or  two  places  for 
the  lava  to  escape,  volcanic  cones  are  built  along  it.  This 
accounts  for  some  of  the  chains  of  volcanic  cones. 

Summary.  —  Great  lava  floods,  rising  tlirougli  fissures,  and  per- 
haps squeezed  ovt  by  mountain  growth,  have  deluged  large  areas 
of  country  in  ivestern  United  States  and  other  I'egions.  Iceland 
has  the  nearest  approach  to  this  condition  at  present.  TJie  clos- 
ing of  most  of  a  fissure  allows  the  formation  of  a  line  of  volcanic 
co7ies. 

94.  Lava  Intrusions.  —  Not  all  the  lava  that  starts  toward  the 
surface  reaches  it.  For  example,  when  eruptions  cease,  the  vent 
of  a  volcano  becomes  filled  with  solid  lava.  This  is  called  the 
volcanic  neck  or  plug  (Figs.  34,  227,  231).  The  long,  narrow  sheets 
filling  the  fissures,  through  which  lava  escapes  on  the  flanks  of  a 
volcano,  are  called  dikes  (Fig.  34).  In  the  neighborhood  of  volca- 
noes, similar  dikes  are  intruded  into  the  rocks  (Fig.  232)  deep  in 
the  earth.  These  and  other  forms  of  intruded  rocks  are  brought 
to  light  by  denudation. 


Fia.  228.  —  Intruded  lava  sheet  forming  the  Palisades  of  the  Hudson.    Notice 
the  columnar  appearance  due  to  jointing.     (See  Fig.  230.) 


Fig.  ^9.  —  Mt.  Tom,  Massachusetts,  a  ridge  formed  by  a  sheet  of  lava  that 
was  intruded  into  the  sandsto-ne  strata  several  geological  ag*^  ago,  then 
Mlte«l  and  warn  into  its  present  mountain  form. 


Fig.  230.  —  Columns  caused  by  the  jointing  of  an  ancient  sheet  of  lava  at  Giant's 
Causeway,  Ireland.  The  columnar  jointing  is  the  result  of  the  breaking  of 
the  lava  as  it  coolsd.     (See  Fior    228.) 


Tig.  231,  — Mato  Tepee,  Wyoming,  a  volcanic  neck  or  plug.    All  the  otlier  ma- 
terial has  been  removed  bv  den'^datian- i'>aving  the  hard  lava  ulusr  stsnn 
^w.v  oVv.^ro  thfl  surround  UK  country      (See    ^so,  Fijpr  ♦jiy'*  > 


VOLCANOES,  EARTHQUAKES,  AND  GEYSERS.        127 


Sheets  of  lava 
have  been  intruded 
between  strata  (Fig. 
34).  Such  intruded 
sheets  or  sills  fre- 
quently have  a  well- 
developed  jointing, 
which  causes  them 
to  break  in  columns, 
usually  with  five  or 
six  sides  (Fig.  230). 
The  Palisades  of 
the  Hudson  (Fig. 
228),  Mts. Tom  (Fig. 
229)  and  Holyoke, 
j\rassachusetts,East 
and  West  Rocks  at 
New  Haven,  Con- 
necticut, the  trap 
mountains  near  Or- 
ange, New  Jersey, 
and  the  lava  sheets 
in  many  other  re- 
gions have  reached 
their  position  by  intrusion  into  the  strata, 

A  large  mass  of  intruded  lava  which  raises  the  strata  to  form  a- 
dome  is  called  a  laccolith,  or  rock  lake  (Figs.  164,  233).  Irregular 
masses  of  intruded  lava  form  bosses  (Fig.  34),  often  made  of  granite. 

These  are  found  in  the  cores  of  old,  worn- 
down  mountains,  as  in  the  Adirondacks, 
New  England,  Scotland,  and  Norway. 


Fig.  232.  —  Dikes  (black)  crossing  a  granite  rock. 


Summary.  —  Various  forms  of  intruded 
igneous  rocks  —  necks,  dikes,  sheets,  lacco- 
liths, and  bosses  —  are  caused  by  the  rising 
of  lava  that  does  not  reach  the  surface.     TJie 

wearing  down  of  the  surface  by  denudation  brings  these  intruded 

lava  masses  to  view. 


Fig.  233.  —  Ideal  section 
through  a  laccolith  (see 
also  Fig.  164). 


128 


NEW  PHYSICAL   GEOGRAPHY, 


95.  Life  History  of  a  Volcano.  —  While  a  volcano  is  active 
the  cone  usually  grows,  because  each  eruption  acids  material 
to  it.  A  dormant  volcano  may,  however,  break  forth  in  so 
violent  an  explosive  eruption  that  the  cone  is  wrecked  and 
its  size  and  form  changed  (Figs.  199,  220).  Or,  by  the  open- 
ing of  a  new  outlet,  the  lava  may  be  drained  from  beneath. 


1  Kilometre 


80RMAV  i  CO.,    N.Y. 


Fig.  234.  —  St.  Paul,  a  volcanic  island  with  the  crater  wall  breached  by  the  waves, 


forming  a  crater  harbor. 


the  cone,  causing  it  to  collapse  (Fig.  219).     But  these  causes 
for  changes  in  the  form  of  volcanoes  are  accidental. 

Throughout  the  life  of  every  volcano  the  agents  of  denu- 
dation are  at  work  tearing  it  down ;  but  so  long  as  it  is 
active,  fresh  supplies  of  lava  or  ash  tend  to  repair  the  dam- 
age. When  the  volcano  becomes  extinct,  however,  denuda- 
tion has  full  sway.  At  first  the  crater  is  occupied  by  a  lake 
(Figs.  216,  225),  but  the  rim  is  slowly  destroyed  and  the 


VOLCANOES,   EARTHQUAKES,   AND  GEYSERS.         129 

lake  drained.  Streams  gully  the  cone  with  deep  ravines 
and  gorges,  until  it  bears  little  resemblance  to  a  volcano. 
As  the  cone  is  slowly  worn  down,  the  hard  core  of  lava  in 
the  volcanic  neck  resists  denudation  better  than  the  looser 
beds  of  porous  lava  and  ash.  It  therefore  remains  abov^e  the 
surface  as  a  central  divide  for  radiating  streams  (Figs.  227, 
231,  237).  In  western  United  States  there  is  every  grada- 
tion from  the  perfect  cone  to  the  volcanic  neck  remnant. 

If  a  volcano  stands  in  the  sea,  the  waves  have  a  large  share  in 
its  reduction  (Fig.  234).  At  first,  steep  cliffs  are  cut,  on  which 
the  waves  beat  with  such  force  that  no  boat  can  land.  As  these 
cliffs  are  pushed  back  into  the  land,  the  crater  may  be  reached 
and  a  crater  harbor  be  opened  (Fig.  234),  Further  wave  cuttir.g 
may  entirely  consume  the  volcano,  leaving  only  a  shoal  to  mark 
its  site. 

Summary.  — -  During  activity  a  volcano  gi'otv.^  hy  addition  of  lava 
or  ash  faster  than  denudation  wears  it  away ;  but  exjylosion  or  col- 
lapse may  change  its  size  or  form.  WJien  extinct,  ho2vever,  volcanoes 
are  slowly  worn  aivay,  the  last  remnant  being  the  hard  volcanic  neck. 
Waves  aid  in  the  destruction  of  cones  in  the  sea. 

96.  Importance  of  Volcanoes.  —  The  most  noticeable  effect 
of  volcanoes  is  the  destruction  of  life,  — human,  plant,  and 
animal.  The  ash,  lava,  steam,  gases,  hot  water,  mud  flows, 
lightning,  and  earthquakes  that  accompany  eruptions  all 
contribute  to  this  destruction.  Nothing  in  nature  is  more 
terrible  than  a  volcanic  eruption. 

Yet  volcanoes  have  some  beneficial  effects.  The  burial  of 
01  ganic  remains  beneath  ash  and  lava  has  preserved  fossils 
that  throw  much  light  on  the  history  of  former  life  on  the 
globe.  The  eruption  of  Vesuvius  in  79  has  preserved  a 
record  of  Roman  life  that  we  could  not  in  any  other  way 
have  obtained.  Lava  flows  have  also  covered  and  preserved 
deposits  of  precious  metal,  as  in  California,  where  some  of 
the  gold  mining  is  carried  on  in  ancient  river  gravels  beneath 
old  lava  flows  (Fig.  238). 


130  NEW  PHYSICAL   GEOGRAPHY, 

Volcarivjes  have  formed  many  lakes,  like  Nicaragua  in  the  Isth. 
mus  of  Panama.  Volcanoes  and  lava  floods  have  helped  make 
grand  scenery.  There  are  few  finer  sights  than  a  large,  snow 
capped  volcanic  cone,  like  Etna,  Ranier,  Hood,  or  Shasta, 

Lava  soils  are  usually  very  fertile ;  for  example,  one  of  the  most 
productive  wheat  regions  of  the  country  is  the  Columbia  valley, 
with  its  rich  volcanic  soil.  Lava  and  ash  have  supplied  much  of 
the  material  of  which  the  sedimentary  strata  are  made ;  and 
igneous  rocks  have  supplied  underground  water  with  much  valu- 
able mineral  for  deposit  in  veins.  Lava  also  heats  the  water, 
thus  giving  it  more  power  to  dissolve  minerals.  The  presence  of 
lava  in  western  United  States  has  had  a  very  important  influence 
on  the  formation  of  the  valuable  mineral  veins  of  that  region. 

Summary.  —  Volcanoes  are  very  destructive  to  life;  but  they  have 
some  beneficial  effects.  They  preserve  records  of  past  life,  and  occa- 
sionally valuable  minerals;  they  cause  lakes;  they  aid  in  the  mak- 
ing of  scenery  ;  their  soils  are  usually  fertile  ;  they  have  helped  sui^ply 
material  for  the  sedimentary  strata;  and  they  have  aided  in  the  for- 
mation of  mineral  veins. 

EARTHQUAKES. 

97.  (A)  Cause.  —  During  mountain  growth  a  jar,  or  earth- 
quake, is  sent  through  the  rocks  when  they  slip  along  fault 
planes.  Sometimes,  as  in  Japan,  in  1891,  the  surface  of  the 
ground  on  one  side  of  a  fault  plane  is  raised  during  the 
shock  (Fig.  239).  Volcanic  explosions,  and  the  rush  of 
lava  into  fissures,  forming  dikes,  also  cause  earthquakes.  In 
fact,  an}^  jar  to  the  rocks,  as  an  explosion  of  gunpowder,  the 
falling  in  of  caverns,  or  an  avalanche,  will  cause  an  earth- 
quake. The  jar  may  be  so  slight  that  it  can  be  detected 
only  by  delicate  instruments;  or  it  may  be  so  violent  as  to 
cause  widespread  destruction. 

(B)  Occurrence.  —  Since  earthquakes  are  so  commonly 
caused  by  the  breaking  of  rocks  and  by  the  movements  of 
lava,  volcanic  regions  are  especially  liable  to  them.     Indeed 


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Fig.  238.  —  Section  of  a  gold  mine  in  California,  beneath  an  ancient  lava  flow 
(volcanic  cap) .  The  circles  indicate  old  river  gravels,  containing  gold,  which 
the  lava  flows  covered. 


Fig.  239.  —  Fault  which  caused  the  earthquake  shock  of  1891  in  Japan.  By  this 
fault  the  road  in  the  middle  of  the  picture  was  raised  several  feet  on  the  far- 
ther side  of  the  fault  plane.     (See  Figs.  241,  242.) 


Fig.  240.  —  A  drawing  to  illustrate  the  movement  of  an  earthquake  wave  outward 
in  all  directions  from  the  focus,  F.  The  shock  reaches  the  surface  first  at  E, 
the  epicentrum,  and  at  later  and  later  periods  on  the  circles  marked  J. 


VOLCANOES,   EARTHQUAKES,   AND   GEYSERS.        131 

a  map  of  the  distribution  of  volcanoes  might  also  serve  as  a 
map  of  frequent  earthquakes.  To  be  sure,  there  have  been 
violent  earthquake  shocks  far  from  volcanoes ;  for  example, 
those  of  Lisbon,  Portugal,  in  1755,  southern  Arkansas  in 
1812,  and  Charleston,  S.C.,  in  1886.  Such  shocks  are  usu- 
ally due  to  the  slipping  of  rocks  along  a  fault  plane. 

(C)  Cliaracteristics.  —  The  center,  or  focus  (Fig.  240),  of  an 
earthquake  may  be  thousands  of  feet  beneath  the  surface.  From 
it  the  jar  passes  through  the  rocks  in  all  directions  (Fig.  240),  in 
much  the  same  way  as  a  shock  passes  through  a  table  when  it  is 
struck  a  heavy  blow.  The  point  above  the  focus,  where  the  shock 
is  first  felt  at  the  surface,  is  called  the  epicentrum. 

At  the  epicentrum  the  movement  of  the  earth  is  vertical,  and 
the  shock  is  most  violent.  As  the  distance  from  the  epicentrum 
increases,  the  shock  is  felt  with  less  and  less  violence.  The 
Charleston  earthquake  was  detected  by  delicate  instruments  as 
far  away  as  Ontario,  Canada. 

In  an  earthquake  shock  the  ground  may  not  rise  and  fall  more 
than  an  inch,  and  yet  do  great  damage.  The  earthquake  is  rarely 
a  single  shock,  but  usually  a  succession  of  jars,  perhaps  near 
enough  together  to  give  the  appearance  of  a  shaking  of  the 
ground.  Very  often  one  earthquake  quickly  follows  another; 
for  example,  in  1783  nearly  1000  shocks  were  felt  in  Calabria,  in 
southern  Italy.  In  this  case  the  rocks  were  probably  slipping 
along  a  fault  plane,  and  each  slip  sent  out  an  earthquake.  The 
many  earthquakes  that  precede  a  volcanic  explosion  are  no  doubt 
due  to  the  breaking  of  the  rocks  by  the  attempt  of  the  steam-filled 
lava  to  escape. 

(D)  Effects. — Violent  earthquakes  are  very  destructive 
(Figs.  241,  242).  They  often  cause  avalanches,  which  dam 
streams  and  form  lakes ;  and  the  shaking  of  the  ground  some- 
times forms  diepressions,  in  which  lakes  and  ponds  gather. 
Trees  are  thrown  down  ;  cracks,  in  which  plants  and  ani- 
mals are  swallowed  up,  are  opened  in  the  ground ;  and  great 
destruction  of  life  is  caused  by  the  overturning  of  houses 


132  NEW  PHYSICAL   GEOGRAPRT, 

{Fig.  241).  In  consequence  of  the  danger  from  falling  houses, 
people  who  live  in  countries  where  earthquakes  are  frequent, 
build  their  houses  so  that  they  will  withstand  ordinary 
shocks.  Even  with  this  precaution,  thousands  of  lives  are 
sometimes  lost  in  a  single  shock.  If  the  shock  is  in  the  sea, 
a  water  wave  may  be  started  which  causes  much  destruction 
on  low  coasts  (p.  186). 

Summary.  —  Earthquakes  are  jars  in  the  rocks,  resulting  from 
faulting,  volcanic  action,  and  other  causes.  Tliey  are  most  common 
in  volcanic  regions,  hut  sometimes  occur  elsewhere.  An  earthquake, 
usually  a  series  of  shocks,  is  most  violent  at  the  epicentrum  {point 
above  the  source,  or  focus,  of  the  shock),  diminishing  in  intensity  in 
all  directions  from  it.  Earthquakes  form  lakes,  open  cracks  in  the 
ground,  and  throw  down  trees  and  houses,  causing  great  destruction 
of  life.     If  in  the  sea,  a  destructive  water  wave  may  he  started. 

HOT   SPRINGS   AND   GEYSERS. 

98.  Underground  water  is  often  heated  by  buried  masses 
of  lava  or  other  causes.  Where  this  heated  water  rises  to  the 
surface,  usually  through  a  fissure,  it  forms  a  hot  spring  ;  and 
if  it  occasionally  gushes  out,  it  is  called  a  geyser. 

The  rising  hot  water  always  bears  mineral  substances  in 
solution,  some  of  which  may  be  deposited  near  the  spring. 
Such  deposits  are  found  around  the  hot  springs  (Figs.  243, 
474)  and  geysers  (Figs.  244,  473)  of  Yellowstone  Park. 
Hot  water  is  sometimes  encountered  in  mines,  and  it  is 
known  that  many  veins  of  gold,  silver,  copper,  and  other 
valuable  metals  have  been  deposited  by  hot  water  on  the 
walls  of  fissures. 

There  are  geysers  in  New  Zealand,  Iceland,  and  "the  Yellow- 
stone National  Park  —  all  volcanic  recfions.  The  mineral  de- 
posits  made  around  these  are  often  very  beautiful  in  form  a^d 
color,  and  they  sometimes  build  a  cone,  through  the  crater 
of  which  the  geyser  erupts  (Figs.  244,  473^. 


Fig.  241. — Destruction  caused  by  the  Japanese  earthquake  of  1891  (Fig.  239;. 
All  this  damage  was  done  to  houses  that  were  built  very  lightly  and  thus 
able  to  withstand  ordinary  earthquake  shocks. 


Fig.  242.  —  Damage  to  a  railroad  bridge  by  the  Japanese  earthquake  of  1891. 
Note  how  the  earth  was  shaken  from  beneath  the  track  where  it  leavea 
the  br>dee 


Fig.  243. —Hot  spring  deposits  in  the  Yellowstone  Park.  These  deposits  are 
carbonate  of  lime  (calcareous  tufa) ,  and  they  build  little  basins  in  which  the 
hot  water  stands,  trickling  over  the  edge  and  forming  icicle-like  deposits. 


Fig.  244.  — Giant  Geyser,  Yellowstone  Park,  in  eruption.     The  deoo^its  made 
around  the  geysers  are  of  silica  (siliceous  sijiter) 


VOLCANOES,   EARTHQUAKES,  AND   GEYSERS.        133  . 

The  geysers  are  exceedingly  interesting.  Old  Faithful 
erupts  every  65  minutes,  with  such  regularity  that  the  time 
i^i  each  outburst-  can  be  accurately  predicted.  With  each 
eruption  a  great  mass  of  hot  water  and  steam  is  thrown  to  a 
height  of  over  100  feet.  The  Minute  Man  geyser  erupts  a 
small  column  every  few  minutes  to  a  height  of  only  a  few 
feet.  Other  geysers  erupt  very  irregularly,  and  some  have 
become  extinct.  The  differences  between  the  geysers  suggest 
the  probability  of  several  explanations  for  their  eruptions. 

Those  that  erupt  regularly,  like  Old  Faithful,  seem  to  be  due  to 
the  following  cause.  There  is  hot  water  in  a  narrow  tube ;  and 
this  is  heated,  perhaps  by  an  adjacent  lava  mass,  until  the  boiling 
point  is  reached.  The  boiling  point  of  water  rises  under  pres- 
sure ;  therefore,  it  may  be  necessary  to  raise  the  temperature  to 
250°  or  more  before  boiling  begins  down  in  the  tube.  When  the 
boiling  point  is  reached  steam  forms,  but  the  narrow  tube  pre- 
vents its  easy  escape.  It  then  lifts  the  column  of  water  and 
causes  some  of  it  to  flow  away  from  the  geyser  crater.  This 
overflow  removes  some  of  the  water  column  and  therefore  reduces 
the  pressure  on  water  that  is  already  boiling  at  250°.  This  re- 
moval of  pressure  at  once  lowers  the  boiling  point ;  and,  since  a 
large  mass  of  water  has  a  temperature  near  250°,  it  suddenly 
changes  to  steam.  This  expels  the  water  with  a  rush.  The 
time  between  eruptions  depends  upon  the  length  of  time  required 
to  heat  the  water  down  in  the  tube  to  the  boiling  point. 

Summary.  —  Hot  water,  rising  from  underground,  forms  hot 
springs  ;  or,  if  it  rises  in  eruption,  geysers.  It  hears  and  deposits 
mineral  substances,  both  at  the  surface  and  in  the  fissures  through 
which  it  rises  —  m  the  latter  case  sometiynes  forming  valuable  min- 
eral veins.     Some  geysers  erupt  regularly,  others  very  irregularly. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  —  80.   Graham  Island.  —  The  eruption  ;   materials 
^.rupted;  the  cone  ;  its  destruction  ;  other  volcanoes. 
81.    Stromboli.  —  Location  ;  size  of  cone  ;  nature  of  eruptions. 


134  NEW  PHYSICAL   GEOGRAPHY. 

82.  Eruptions  of  1902  in  the  West  Indies.  — Destruction  of  St.  Pierre; 
La  Soufriere  ;  previous  eruptions  ;  warnings  ;  eruption  of  May  8 ;  causo 
of  destructiveness ;  effects  of  later  eruptions ;  material  erupted ;  distri- 
bution of  ash  ;  mud  flows  ;  probable  future. 

83.  Vesuvius.  —  (a)  Eruption  of  79  :  previous  condition  ;  settlements 
on  slopes  ;  warnings  ;  effect  of  eruption  ;  our  knowledge  of  the  eruption  ; 
conditions  accompanying  eruption.  (6)  Pompeii  :  importance  of  its  ex- 
cavation, (c)  Condition  since  79:  difference  in  eruptions;  present 
condition;  ordinary  quiet ;  increase  in  activity  ;  lava  eruptions;  observa- 
tory,    (f/)  Other  volcanoes  of  Bay  of  Naples. 

84.  Etna.  —  Position  ;  eruptions  ;  great  height ;  decay  of  the  lava. 

85.  Krakatoa.  —  Former  eruption  ;  eruption  of  1883  ;  ash  on  the  sea ; 
air  wave  ;  water  w^ave  ;  conditions  since  eruption  ;  future. 

86.  Hawaiian  Volcanoes.  —  (a)  Island  of  Hawaii:  its  volcanoes;  its 
height.  (&)  The  craters:  lava  lakes;  calderas.  (c)  Lava  flows:  rising 
in  crater;  draining  through  fissures  ;  length  of  flows  ;  nature  of  flow. 

87.  Mt.  Shasta  and  Lassen  Peak.  —  Shasta ;  ash  cone ;  recent  eruptions. 

88.  Crater  Lake.  — ■  Size  of  lake  ;  cause  of  caldera. 

89.  Materials  Erupted.  —  Steam  ;  other  gases ;  meaning  of  "  smoke  "  and 
"  flame  ";  lava  flows  ;  effect  of  steam  explosion  on  lava ;  bombs  ;  mud  flows. 

90.  The  Forms  of  Volcanic  Cones.  —  Ash  cones;  lava  cones;  ash  and 
lava  cones;  calderas;  wrecked  cones. 

91.  Distribution  of  Volcanoes.  —  Number ;  general  location ;  belt 
encircling  Pacific,  —  South  America,  Antilles,  western  United  States, 
Aleutian  Islands,  eastern  Asia  ;  other  chains,  —  Pacific  and  Indian  oceans, 
continents,  Mediterranean,  open  Atlantic;  areas  free  from  volcanoes; 
areas  of  extinct  volcanoes  ;  association  with  mountains. 

92.  Cause  of  Volcanoes.  —  Immediate  cause ;  effect  of  growing  moun- 
tains ;  condition  in  western  United  States. 

93.  Lava  Floods.  —  (a)  Columbia  valley:  cause;  area;  lava  plateau; 
thickness;  later  tilting,  (b)  Other  areas,  (c)  Present  condition  :  general 
•absence  of  lava  floods  ;  Iceland;  relation  of  fissures  to  volcanic  cones. 

94.  Lava  Intrusions.  —  Volcanic  necks  ;  dikes  ;  how  revealed  ;  sheets 
or  sills;  illustrations:  laccoliths;  bosses. 

95.  Life  History  of  a  Volcano.  —  Normal  growth  ;  effects  of  explosion  ; 
of  collapse ;  denudation  ;  the  volcanic  neck  ;  volcanoes  in  the  sea. 

96.  Importance  of  Volcanoes.  —  Destruction  of  life ;  preservation  of 
fossils ;  oi  human  records  ;  of  mineral ;  formation  of  lakes  ;  effect  on 
scenery;  on  soils;  on  sedimentary  rocks;  on  mineral  veins. 

97.  Earthquakes.  —  (A)  Cause:  faults;  volcanic  action;  other 
causes.  (B)  Occurrence:  volcanic  regions;  other  regions ;  illustrations. 
(C)  Characteristics:  focus;  nature  of  shock ;  epicentrum;  distance  trav- 


VOLCANOES,   EARTHQUAKES,   AND   GEYSERS.        136 

eled ;  repeated  shocks ;  explanation  of  repeated  shocks.  (D)  Effects : 
avalanches ;  lakes ;  cracks  in  the  ground ;  overturning  houses ;  sea  waves. 

98.  Hot  Springs  and  Geysers.  —  Cause ;  nature  of  geysers ;  mineral  de- 
posit at  surface ;  mineral  veins ;  distribution  of  geysers  ;  geyser  deposits ; 
eruption  of  geysers ;  explanation  of  geyser  eruptions. 

Questions,  —  80.  State  the  history  of  Graham  Island.  What  causes 
ash  and  pumice?     How  do  many  volcanoes  differ  from  this  one? 

81.  Where  is  Stromboli?     State  its  characteristics  as  a  volcano. 

82.  What  reasons  were  there  for  expecting  an  eruption?  Why  was 
the  eruption  so  destructive  at  St.  Pierre?  What  were  its  effects?  What 
was  the  nature  of  the  material  erupted ?     What  causes  mud  flows? 

83.  What  was  the  condition  of  Vesuvius  in  79  ?  Tell  about  the 
eruption  of  79.  How  has  it  been  of  importance?  What  has  been  the 
subsequent  history  of  Vesuvius?  What  is  its  present  condition  ?  What 
other  signs  of  volcanic  activity  are  there  near  Vesuvius? 

84.  Describe  Etna  and  its  eruptions. 

85.  Describe  the  eruption  of  Krakatoa  and  its  effects. 

86.  Describe  the  Hawaiian  volcanoes  and  craters.  Describe  the  erup- 
tions.    What  is  the  nature  of  the  lava  flows? 

87.  What  is  the  condition  of  Shasta?    Near  Lassen  Peak? 

88.  What  has  been  the  history  of  Crater  Lake  ? 

89.  What  substances  are  erupted  from  volcanoes? 

90.  How  do  ash  and  lava  cones  differ?    Why?     What  are  calderas? 
9L    Trace  (Fig.  222)  the  principal  chains  of  volcanoes  (nam*ed  in  text) 

in  the  belt  which  partly  encircles  the  Pacific.  Where  else  are  volcanic 
chains  found?     Are  volcanoes  found  everywhere  ? 

92.  What  is  the  immediate  cause  for  volcanic  eruptions?  What  rela- 
tion is  there  between  growing  mountains  and  volcanoes? 

93.  Describe  the  lava  floods  of  the  Columbia  valley.  Where  else  were 
lava  floods  formed?     How  may  volcanic  cones  succeed  fissure  eruptions? 

94.  What  are  volcanic  necks?  Dikes?  Sheets  or  sills ?  Give  illustra- 
tions.    What  are  laccoliths?    Bosses?     How  are  they  brought  to  light? 

95.  What  may  affect  the  form  of  a  volcano  before  its  extinction  ? 
What  is  its  history  after  extinction?    What  is  the  case  in  the  sea? 

96.  State  the  important  effects  of  volcanoes. 

97.  (A)  What  are  the  causes  of  earthquakes?  (B)  Where  are  they 
most  frequent ?  Why?  What  explains  violent  earthquakes  elsewhere? 
(C)  What  is  the  focus?  The  epicentrum?  What  is  the  nature  of  the 
shock?     (D)  What  are  the  effects  of  earthquakes ? 

98.  What  are  hot  springs  and  geysers?  What  do  the  waters  carry? 
Where  are  geysers  found?  How  do  they  vary?  Give  the  explanation 
of  regularly  erupting  geysers. 


136  JSTEW  PHYSICAL   GEOGRAPHY. 

Suggestions.  —  (1)  Illustrate  the  formation  of  volcanoes.  Take  an 
ordinary  wooden  box,  for  example  a  soap  or  shoe  box,  remove  the  cover 
and  turn  it  on  its  side  with  the  bottom  toward  the  class  and  the  open 
side  toward  the  teacher.  Extend  a  glass  tube  through  the  top  of  the  box 
and  blow  sand  gently  through  it.  A  cone  will  be  built  with  a  crater  in 
the  center.  The  force  of  the  eruption  njay  be  made  to  vary,  and  many 
phases  of  volcanic  eruptions  may  be  imitated.  The  sand  is  best  blown 
through  by  means  of  foot  bellows,  and  the  result  will  be  more  satis- 
factory if  the  lower  part  of  the  tube  is  expanded  into  a  bulb  that  is 
partly  filled  with  sand.  (2)  In  the  same  way,  force  melted  wax  up  to 
form  a  volcano.  Have  a  branch  tube  extend  oif,  reaching  an  inch  or  two 
above  the  top  of  the  box.  Keep  its  end  plugged  until  the  wax  covers  it, 
then  open  it  and  plug  the  main  tube,  allowing  the  wax  to  escape  through 
the  side  tube  to  illustrate  the  eruption  of  lava  from  the  sides  of  a  cone. 
If  the  wax  solidifies  in  the  tube  and  interferes  with  the  experiment, 
warm  the  tube.  (3)  With  a  little  ingenuity  wax  can  be  forced  between 
layers  of  clay  and  cardboard,  forming  laccoliths;  or  into  fissures  cut 
through  the  layers,  forming  dikes.  (4)  Look  for  dikes.  If  your  home  is 
along  the  rocky  coast  of  New  England,  they  may  easily  be  found.  Study 
them  and  tell  what  you  observe.  (5)  Students  in  the  Connecticut  valley, 
New  York  City,  and  east  central  New  Jersey  should  be  given  an  excur- 
sion for  the  study  of  the  trap  sheets.  Look  for  jointing.  Look  for  the 
rock  strata  above  or  below  the  lava.  How  do  they  differ  from  the  trap? 
Make  careful  observations.  (6)  Earthquakes  may  be  imitated  and 
studied  by  jarring  a  slab  or  stone  or  a  table  top.  (7)  A  geyser  eruption 
may  be  made  by  constructing  a  long  (two  or  three  feet),  narrow  tube,  fill- 
ing it  with  water,  aiid  heating  it  near  the  bottom  until  steam  is  produced. 

Reference  Books.  —  Russell,  Volcanoes  of  North,  America,  Macmillan 
Co.,  N.Y.,  1897,  $1.00  ;  Heilprin,  Mt.  Pelee  and  the  Tragedy  of  Martinique, 
Lippincott,  Philadelphia,  1903,  |3.00;  Hull,  Volcanoes,  Scribner's  Sons, 
N.Y.,  1892,  -11.50;  Judd,  Volcanoes,  Appleton  &  Co.,  N.Y.,  1881,  $2.00; 
Dana,  Characteristics  of  Volcanoes,  Dodd,  Mead  &  Co.,  N.Y.,  1891,  |5.00 ; 
Lyell,  Principles  of  Geology,  Chapters  XXIII-XXV,  Appleton  &  Co., 
N.Y.,  1877,  18.00;  Bonney,  Volcanoes,  Putnam's  Sons,  N.Y.,  1899,  $2.00; 
Geikie,  Ancient  Volcanoes  of  Great  Britain,  2  vols.,  Macmillan  Co.,  N.Y., 
1897,  $11.25;  Dutton,  Hatvaiian  Volcanoes,  4:th  Annual  U.  S.  Geological 
Survey,  p.  8  ;  Gilbert,  Geology  of  the  Henry  Mountains,  Washington, 
1877  (out  of  print)  ;  Diller,  Mt.  Shasta,  National  Geographic  Mono- 
graphs, American  Book  Co.,  N.Y.,  1895,  $2.50;  Diller,  Crater  Lake, 
Annual  Report,  Smithsonian,  Institution,  1897,  p.  369;  Milne,  Earth- 
quakes, Appleton  &  Co.,  N.Y.,  1891,  $1.75;  Dutton,  Charleston  Earth- 
quake, 9th  Annual  U.  S.  Geological  Survey,  p.  209 ;  Weep,  Hot  Springs, 
9th  Annual  IJ.  S.  Geological  Survey,  p.  619. 


Fig.  245.  —  A  snow  field  in  tlie  Alps  —  the  top  of  Mt.  Blanc. 


Fig.  246,  — a  ne've  region  in  the  Alps,  showing  the  slope  from  which  the  snow 
slides,  and,  in  the  foreground,  the  crevassed  neve. 


Fig.  247.  —  The  Mer  de  Glace,  an  Alpine  glacier.     A  band  of  lateral  moraine  i§ 
Seen  on  tl.e  left,  and  a  talus,  down  which  moraine  material  comes,  on  the  right. 


Fig.  248.  —  Crevasses  in  a  Swiss  glacier  in  the  neve  region. 


^ 


Fig.  249.  —  Snow  field  and  jrlacier  in  the  Alps  witn  lateral  and  medial  moraine 


?m.  250.  — A  valley  glacier  in  Alaska,  showing  well-defined  medial  moraine; 
■Use  the  snow  field  high  up  in  the  mountaias. 


CHAPTER   yill. 

GLACIERS    AND   THE   GLACIAL   PERIOD. 

99.  Valley  Glaciers.  —  The  snow  line  in  the  Alps  is  about 
9000  feet  above  sea  level.  Above  this  line  is  a  great  snoiv 
field  (Fig.  245,  249),  in  which  snow  accumulates  year  after 
year,  in  some  places  reaching  a  depth  of  hundreds  of  feet. 
Some  of  the  snow  is  whirled  away  by  the  wind,  settling  in  val- 
leys ;  some  slides  down  the  steeper  slopes  (Fig.  246),  as  snow 
slides  from  the  roof  of  a  house.  There  is  so  much  snow 
falling  into  the  valleys,  both  as  small  slides  and  great  ava- 
lanches, that  they  would  be  completely  filled  if  it  could  not 
in  some  way  be  removed. 

The  snow  that  accumulates  in  the  valleys  gradually  changes 
lo  granular  snow  ice,  resembling  the  snow  banks  of  late  win- 
ter. .This  change  is  partly  due  to  the  pressure  of  the  over- 
lying mass,  and  partly  to  alternate  melting  and  freezing  dur- 
ing summer  days  and  nights.  The  granular  ice,  called  the 
neve  (Figs.  246,  248),  moves  slowly  down  the  steep  valleys. 

As  the  mass  moves,  pressure  and  further  melting  and  freez- 
ing gradually  change  it  to  pure,  clear  ice.  The  supply  from 
the  snow  field  causes  the  ice  to  move  down  the  valley,  much 
as  a  river  extends  beyond  the  place  where  the  rain  fell.  Such 
an  ice  tongue,  occupying  a  valley,  is  called  a  valley  glacier 
(Figs.  15T,  181, 185,  247-251).  In  the  Alps  some  of  the  gla- 
ciers are  10  to  15  miles  long,  extending  4000  or  5000  feet  below 
the  snow  line.  They  end  where  the  warmth  is  sufficient  to 
completely  melt  the  ice,  and  the  terminus  may  be  below  the 
timber  line,  even  in  the  zone  where  grain  will  grow. 

The  glacier  moves  down  grade,  behaving  much  as  a  mass 

137 


138  NEW  PHYSICAL   GEOGRAPHY, 

of  wax  does  when  under  pressure ;  that  is,  it  moves  as  if 
it  were  slowly  flowing.  The  most  rapid  motion  is  near  the 
middle,  though  even  here  it  does  not  usually  move  more 
than  two  feet  a  day.  Every  glacier  carries  rock  fragments, 
some  of  which  have  fallen  from  the  valley  sides,  while  others 
have  been  obtained  from  its  bed.  These  fragments,  slowly 
dragged  along,  and  pressed  down  by  the  weight  of  the  ice, 
groove,  striate,  and  scour  the  rocks  over  which  the  glacier 
moves.  It  may  be  compared  to  the  work  of  sandpaper.  By 
this  scouring,  known  as  glacial  erosion^  valleys  are  both  deep- 
ened and  broadened. 

Bands  of  rock  fragments,  accumulated  on  the  margin  of 
the  glacier,  where  they  have  fallen  from  the  cliffs,  are  known 
as  lateral  moraines  (Figs.  247,  249).  Where  two  glaciers  join, 
two  lateral  moraines  unite,  forming  a  medial  moraine  (Figs. 
249,  250),  near  the  middle  of  the  glacier.  The  surface  of  the 
glacier  melts  in  summer  ;  but  moraines  protect  the  ice  be- 
neath from  melting,  and  this  causes  them  to  stand  up  as 
ridges,  often  50  feet  or  more  above  the  surface  of  the  glacier. 

Although  ice  under  steady  pressure  slowly  flows,  when  subjected 
to  a  decided  strain  it  breaks,  forming  cracks,  or  crevasses'  (Figs. 
246,  248),  in  the  glacier.  Where  the  valley  bottom  is  irregular, 
causing  many  strains  in  the  moving  ice,  crevasses  are  especially 
abundant ;  and  when  the  slope  of  the  bottom  is  steep,  the  ice  may 
become  so  crevassed  that  it  is  almost  impossible  to  pass  over  it. 
Such  a  section  is  called  an  ice  jhll.  Moraine  fragments  are  con- 
stantly falling  into  these  crevasses,  some  of  them  finding  their 
way  to  the  bottom  of  the  glacier.  Water  from  the  melting  ice  also 
falls  into  crevasses,  boring  pot  holes  (p.  54)  in  the  rock  floor,  and 
flowing  in  ice  tunnels  to  the  front  of  the  glacier. 

The  rock  fragments  frozen  in  the  bottom  of  a  glacier  aru 
known  as  the  ground  moraine^  and  when  a  glacier  disappears 
by  melting  this  is  left  as  a  deposit  on  the  valley  bottom.  To 
it  are  added  the  materials  of  the  lateral  and  medial  moraines, 
which  slowly  settle  to  the  ground  as  the  glacier  melts. 


GLACIERS  AND   THE  GLACIAL  PERIOD.  139 

At  the  end,  or  terminus,  of  a  glacier,  rock  fragments  are 
built  into  a"  terminal  moraine.  These  fragments  are  brought 
by  the  ice  and  loosened  as  it  melts,  accumulating  in  irregular 
piles  at  the  base  of  the  glacier  front.  If  the  end  of  a  gla- 
cier remains  in  one  place  for  a  long  time,  the  terminal  moraine 
hills  may  reach  a  height  of  100  or  200  feet. 

The  water  that  falls  into  crevasses  emerges  as  a  stream 
from  the  ice  front  (Fig.  185),  often  from  an  ice  cave.  It  is 
white  with  suspended  sediment,  or  rock  flour ^  supplied  by  the 
grinding  up  of  rocks  beneath  the  glacier.  In  summer,  the 
volume  of  these  glacier  streams  becomes  so  great  that  even 
pebbles  are  moved  along.  The  clay  is  carried  far  down  the 
valley,  but  the  sand  and  pebbles  are  usually  deposited  on  the 
valley  bottom,  gradually  filling  the  valley.  Over  this  deposit 
the  stream  flows  in  a  branching,  braided  course,  constantly 
depositing  sediment  and  changing  position  (Fig.  251).  Such 
ivash  deposits  may  reach  a  depth  of  over  100  feet. 

Summary.  —  Snow,  derived  from  the  snow  field,  accumulates  in  the 
valleys,  changing  to  granular  ice  {neve),  then  to  ice,  which  extends 
down  the  valley  as  an  ice  tongue  or  valley  glacier.  As  it  moves, 
it  scours  its  bed,  aiid  carries  rock  fragments,  both  on  its  surface 
(lateral  and  medial  moraines)  and  at  its  bottom  {ground  moraine). 
Both  rock  fragments  and  icater  descend  to  the  bottom  of  glaciers 
through  crevasses,  caiised  by  strains  resulting  from  the  ice  motion. 
The  rock  fragments  form  a  ground  moraine  and  assist  the  ice  in 
erosion;  the  water  emerges  from  beneath  the  ice  in  streams,  bearing 
rock  four,  sand,  and  pebbles,  ichich  build  extensive  icash  deposits 
Terminal  moraines  are  built  at  the  ice  front. 

100.  Glaciers  of  Alaska.  —  Of  the  many  Alaskan  glaciers 
the  best  known  is  the  immense  Muir  glacier  (Figs.  253-255), 
which  is  fed  by  twenty  glacier  tributaries  or  more.  These 
unite  to  form  an  ice  tongue  which  advances  down  a  broad 
valley  and  ends  in  the  sea.  Its  front  is  a  cliff,  rising  200 
feet  above  the  water  and  extending  700  or  800  feet  below. 
From  it  small  icebergs  frequently  break  off  and  float  down 


NEW  PHYSICAL  GEOGRAPHY. 


the  bay.     The  discharge  of  icebergs,  added  to   melting,   is 
causing  the  Muir  glacier  to  steadily  grow  shorter. 


Fig.  252.  — The  Malaspina  glacier 

Farther  north  is  another  large  glacier,  the  Malaspina  (Fig. 
252),  formed  by  the  union  of  a  number  of  valley  glaciers  that 
descend  from  the  Mt.  St.  Elias  range  (Fig.  256).  This  glacier 
spreads  out,  fan-shaped,  on  a  plain  at  the  base  of  the  mountains. 
For  this  reason  it  is  called  a  Piedmont  glacier  (from  jt??W,  foot, 
and  mont,  mountain).  It  has  a  length  of  60  or  70  miles  and 
a  breadth  of  20  or  25  miles;  and  its  movement  is  so  slow  that 
it  is  an  almost  stagnant,  undulating  ice  plateau  (Fig.  257). 

Melting  ard  evaporation  have  caused  the  rock  fragments  in  the 
upper  portion  of  the  glacier  to  accumulate  at  the  surface,  espe- 
cially near  the  lower  end.  These  rock  fragments  form  a  rocky 
soil  on  the  glacier,  in  which  a  forest  is  growing  (Fig.  258). 

Summary.  —  3Iuir  glacier,  fed  by  over  Urenty  trihntary  glaciers, 
ends  in  sea  cliffs  from  which  icebergs  are  discharged.  Malasi}ina 
glacier^  an  almost  stagnant  ice  plateau,  is  called  a  Piedmont  glacier. 


k. 


Fig.  253.  —  The  sea  front  of  Muir  glacier,  Alaska. 


Fig-  254.  — The  end  of  Muir  glacier 


Fig.  255.  —  The  crevassed  top  of  Muir  glacier. 


liG.  256  —  Mt    St    Elias,  Alaska,  from,  which  valley  glaciers  descend  to  join 

the  Malaspina  glacier. 


Fig.  257.  — The  surface  of  Malaspiua  glacier,  Alaska. 


ViG.  258.  —  Terminus  of  the  Malaspina  glacier  on  the  land.    This  is  an  ice  cliff 
■^^oraii  with  moraine  soil,  on  the  top  of  which  a  forest  is  growing. 


GLACIERS  AND   THE  GLACIAL  PERIOD.  141 


\ 


101.  Distribution  of  Valley  Glaciers.  —  There  are  several  liuiidred 
valley  glaciers  in  Switzerland,  and  these  serve  as  one  of  the  attrac- 
tions to  tonrists.  There  are  also  many  in  the  Cancasus  and  Hima- 
laya mountains,  and  in  Norway,  where  some  descend  to  the  sea. 

There  are  small  glaciers  in  some  of  the  high  mountain  valleys 
of  Mexico  (in  the  tropical  zone)  and  of  western  United  States. 
Toward  the  north  glaciers  increase  in  size  and  number,  becoming 
especially  large  and  abundant  in  western  Canada  and  Alaska. 
Tourists  are  beginning  to  visit  the  Selkirk  range  of  western 
Canada,  which  rivals  Switzerland  in  the  grandeur  and  beauty  of 
its  snow-capped  mountains  and  its  glaciers.  The  Muir  glacier  is 
also  regularly  visited  by  steamer. 

The  islands  of  the  Arctic,  such  as  Baffin  Land,  Iceland,  and 
Spitzbergen,  have  innumerable  valley  glaciers,  many  of  which 
descend  to  the  sea.  Glaciers  are  also  abundant  in  New  Zealand 
and  the  southern  Andes. 

Summary.  —  Valley  glaciers  exist  in  many  parts  of  the  loorld, 
eveyi  in  the  tropical  zone.  In  cold  climates  they  occupy  loio  valleys, 
and  even  descend  to  the  sea;  in  warm  climates  they  are  confined  to 
the  upper  valleys  of  high  mountains. 

102.  Former  Extension  of  Valley  Glaciers.  —  It  is  well 
known  that  valley  glaciers  were  formerly  more  extensive  than 
at  present.  In  fact,  they  once  existed  in  places  where  now 
there  aje  none.  Nearly  all  Switzerland  was  once  covered  by 
an  ice  sheet,  formed  by  the  union  of  valley  glaciers;  there 
were  many  in  the  Rocky  Mountains ;  and  glaciers  existed 
even  in  the  Adirondacks  and  New  England  mountains. 

The  clear  evidence  of  this  former  extension  of  glaciers  is  of 
various  kiads,  as  follows  :  (1)  rock  fragments,  called  erratics 
(Fig.  259),  often  weighing  tons,  are  found  in  the  valleys. 
In  many  cases  they  are  different  from  the  rock  near  by,  but 
are  the  same  as  rock  found  higher  up  the  valley.  They  have 
apparently  been  brought  by  some  powerful  agent,  like  ice. 

(2)  The  ledges  in  the  valleys  have  been  polished  and 
scratched    by  the   dragging   of   rock   fragments  over  them 


142  NEW  PHYSICAL   GEOGRAPHY. 

(Fig.  259),  as  if  by  ice.     These  scratches,  or  strice,  extend  in 
the  direction  in  which  the  erratic  hoivlders  have  been  carried. 

(3)  Deposits  like  those  now  being  made  by  glaciers  occur 
in  the  valleys  (Figs.  251,  260).  These  include  lateral,  medial, 
terminal,  and  ground  moraines,  the  ground  moraine  making 
a  thin  sheet  of  mixed  clay,  pebbles,  and  bowlders,  called  bowl- 
der clay  or  till.  This  till  is  unlike  water  deposits,  being 
unassorted  and  unstratified ;  but  it  is  like  deposits  from  ice, 
which  carries  and  drops  large  and  small  fragments  with  equal 
ease,  and,  therefore,  side  by  side.  In  front  of  the  terminal 
moraines,  and  sometimes  mixed  with  them,  are  wash  deposits 
of  stratified  gravels,  like  those  now  being  laid  dowji  by  the 
streams  that  issue  from  glaciers. 

(4)  The  valleys  also  show  signs  of  glacial  erosion  (Figs.  251, 
259,  261,  262).  The  rocks  of  their  sides  and  bottoms  are  polished 
by  ice  scouring,  and  the  ledges  are  worn  into  smooth,  rounded 
curves,  known  as  roches  moutonnees  (sheep  backs).  This  erosion 
has  often  broadened  and  deepened  valleys  (Fig.  261);  and  where 
they  have  been  deepened  a  little  more  than  elsewhere,  i^ock  basins 
have  sometimes  been  formed,  now  occupied  by  lakes  and  ponds. 
In  some  cases  the  valleys  have  been  deepened  hundreds  of  feet ; 
and  in  the  region  of  former  neve,  broad  deep  amphitheaters, 
called  cirques,  have  been  formed. 

Since  the  ice  disappeared,  side  streams  tributary  to  these  ice^ 
eroded  valleys  have  not  had  time  to  cut  their  bottoms  clown  to 
the  level  of  the  deepened  main  valleys.  Their  bottoms  therefore 
stand  above  the  level  of  the  main  valley,  and  they  are  accordingly 
called  hanging  valleys  (Fig.  293).  From  them  the  streams  tumble 
into  the  main  valley  as  falls  or  rapids.  These  waterfalls  add  to 
the  charm  of  the  mountain  scenery  in  Switzerland,  Norway, 
Alaska,  and  other  regions  from  which  glaciers  have  departed. 

Summary.  —  Erratics,  strice,  moraines,  till,  and  wash  dejiosits  are 
among  the  evidences  that  valley  glaciers  were  formerly  more  extensive, 
and  even  existed  where  noiv  there  are  none.  Evidences  of  ice  erosion 
are  also  foiLnd,  in  the  form  of  roches  moutonnees,  broadened  and  deep- 
ened valleys,  rock  basins,  cirques,  and  hanging  valleys. 


Fig.  259.  —  The  top  of  a  Swiss  glacier,  showing  crevasses.  Beyond  it  is  a 
smoothed,  P'^ratched  rock  surface  with  erratic  bowlders  on  it.  The  ice  has 
left  this  surface  so  recently  that  vegetation  has  not  had  time  to  occupy  it. 


Fia.  260.  -  -  Moraines  and  moraine  lakelets  in  a  Rocky  Mountain  valley,  in  which 

a  valley  glacier  formerly  existed. 


tiG.  261.— 


Lauterbrunnen  valley  and  fall,  Switzerland,  a  valley  down  which  a 
glacier  formerly  extended,  deepening  it. 


Fi«.  262.  —  A  view  on  the  Grimsel  Pass,  Switzerland,  showing  a  smoothed  rock 
valley  with  little  lakes.  This  was  formerlv  occupied  by  a  glacier  which 
has  BOW  pntlrf^lv  disappeared^  leaving  scwwed  leot'-k  svi«»«,9jrni  rrowj.iTvo  hIo 


GLACIERS  AND   THE  GLACIAL  PEBIOB. 


148 


103.  The  Greenland  Ice  Sheet.  —  The  island  of  Greenland 
is  mountainous,  not  greatly  unlike  northern  New  England 
and  Scotland.  Near  the  coast  there  is  a  fringe  of  peninsulas 
and  islands  on  which  there  are  scattered  Eskimo  settle- 
ments. The  mountain  valleys  have  valley  glaciers,  and  small 
ice  caps  exist  on  some  of  the  larger  islands  and  peninsulaSv 


Fig.  263.  —  A  map  of  the  region  around  the  Cornell  glaciei*  where  Figs.  264,  265, 
and  271  were  taken  (near  the  long  peninsula  at  the  top).  The  arrows  show 
the  general  movement  of  the  ice,  outward  from  the  interior,  but  turning 
down  into  the  valleys,  and  ending  in  tongues  in  the  bays  and  fiords. 

Back  of  the  fringe  of  coast  land  is  a  great  waste  of  ice  and 
snow,  with  an  area  of  about  500,000  square  miles,  moie 
than  ten  times  the  area  of  New  York  State.  This  enormous 
ice  cap  is  sometimes  called  the  Greenland  glacier;  but  it  is 
so  large,  and,  in  a  number  of  ways,  so  diflterent  from  what 
is  commonly  called  a  glacier,  that  the  term  ice  sheet  is  a 
better  name.  An  ice  sheet  is  a  mass  of  ice,  covering  and 
moving  over  a  large  area  of  land,  Idll  and  valley  alike. 


144  NEW  PHYSICAL   GEOGRAPHY. 

In  the  interior,  a  part  of  which  Peary  has  crossed,  the 
elevation  is  8000  to  10,000  feet,  and  the  temperature 
never  rises  above  the  freezing  point.  The  surface  is, 
therefore,  always  covered  with  loose,  dry  snow.  Nearer 
the  coast,  where  the  elevation  is  less,  the  warmth  of  the 
summer  sun  melts  the  snow,  leaving  an  ice  surface  quite 
like  that  of  valley  glaciers. 

The  continued  fall  of  snow  on  the  high  interior  of  Green- 
land has  caused  such  an  accumulation  that,  changed  to  ice 
by  pressure,  it  is  forced  to  move  slowly  outward  (Fig.  263) 
in  all  directions,  —  north,  east,  south,  and  west.  It  moves 
as  a  great  pile  of  wax  would,  and  in  its  slow,  irresistible 
outward  movement  crosses  hill  and  valley  alike. 

Back  of  the  coastal  fringe  the  only  land  that  appears  is  an 
occasional  high  mountain  peak,  called  a  nunatak  (Fig.  264), 
which  projects  like  an  island  above  the  sea  of  ice.  Near  the 
coast  the  ice  extends  down  the  valleys,  often  reaching  the 
sea  (Figs.  263,  264).  At  the  head  of  fiords  these  valley 
tongues  end  in  sea  cliffs  200  or  300  feet  high  (Fig.  265), 
advancing  in  some  cases  at  the  rate  of  from  50  to  75  feet  a 
day,  and  discharging  huge  icebergs  that  float  into  the  Arctic 
(Figs.  267,  268,  339).  Most  of  these  tongues  are  only  a 
few  miles  wide ;  but  the  largest  of  all,  the  Humboldt  glacier 
of  north  Greenland,  is  60  miles  wide.  Their  surface  is 
broken  by  crevasses,  quite  unlike  the  smooth,  unbroken  ice 
plateau  of  the  interior. 

Unlike  that  of  valley  glaciers,  the  surface  of  the  ice  sheet 
is  quite  free  from  rock  fragments,  excepting  where  nunataks 
supply  materials  for  a  medial  moraine,  or,  near  the  end  of  a 
valley  tongue,  where  cliffs  rise  from  the  ice  margin.  Near 
the  bottom,  however,  there  is  much  rock  material,  which  has 
been  worn  from  the  land.  In  transporting  this  load  of  rock 
fragments  at  its  base,  the  ice  sheet  scours  its  bed  and  does 
much  work  of  erosion. 

Melting  near  the  margin  causes  streams  and  even  ponds 


Fig.  264.  —  A  view  of  the  Greenland  ice  sheet,  showing  its  vast  expanse,  its 
extension  into  the  fiord  valleys,  and  a  nunatak  rising  above  its  surface. 
This  is  a  view  of  the  Cornell  glacier,  one  of  the  large  valley  tongues  of  the 
Greenland  ice  sheet. 


Fig.  265.  — Front  of  the  Cornell  glacier  rl^'ig.  264).  where  it  advances  into  the 
^ord.    From  it  huge  iceberg  arp  frequently  dischargei.!.. 


Fig.  266.  —  A  wash  plain  deposit  made  by  water  at  the  margin  of  a  Green- 
land glacier.     (Compare  with  Figs.  272  and  275.) 


Fig.  267.  —  An  iceberg  aground  near 
Fig.  264. 


Fig.  268.  —  A  tunnel  in  Fiy.  267.  perhaps 
an  old  stream  chauuel  in  the  "ice. 


GLACIERS  AND   THE  GLACIAL  PEBIOD,  145 

to  form  on  top  of  the  ice;  and  this  water  finds  its  way  by 
crevasses  to  the  bottom.  Where  this  water  emerges,  either 
on  the  land  or  in  tlie  sea,  deposits  of  gravel  and  clay  are 
being  made  (Figs.  266,  272).  Along  the  ice  front,  too, 
moraines  are  being  built  of  rock  fragments  loosened  by  melt- 
ing (Fig.  271).  Many  of  these  are  worn  and  scratched  (Fig. 
290)  by  the  grinding  they  have  received. 

There  is  good  evidence  that  the  Greenland  ice  sheet,  like  valley 
glaciers,  once  extended  much  farther,  completely  covering  some, 
if  not  all,  of  the  islands  and  peninsulas.  This  evidence  is  sup- 
plied by  moraines,  erratics,  glacial  scratches,  rounded  and  deep- 
ened valleys,  and  rock  basins.  The  Greenland  ice  sheet,  like  the 
Muir  and  many  other  glaciers,  is  now  melting  back. 

Summary.  —  Greenland  is  covered  by  a  great  ice  sheet,  with  a 
fringe  of  land  near  the  coast,  and,  near  the  margin,  occasional  nuna- 
taks  projecting  above  the  ice.  From  the  high  interior,  where  snow 
falls  summer  and  winter,  there  is  a  movement  outward  in  all  direc- 
tions, the  7nargin  of  the  ice  consisting  of  valley  tongues,  often  ending 
in  the  sea  into  ivhich  icebergs  are  discharged.  Tlie  ice  has  little  rock 
material  on  the  surface,  but  carries  much  near  the  bottom,  ivith  which 
it  is  doing  ivork  of  erosion  and  making  moraine  and  tvash  deposits. 

104.  Other  Ice  Sheets.  —  Qn  the  Antarctic  continent  there  is  an 
enormous  ice  sheet,  of  which  little  is  known.  It  is  generally 
believed  that  the  entire  South  Polar  region  is  covered  by  an  ice 
cap,  with  an  area  larger  than  the  United  States.  For  a  long  dis- 
tance its  margin  is  a  great  ice  wall,  rising  several  hundred  feet 
above  the  sea  and  discharging  huge  tabular  icebergs. 

On  the  larger  islands  of  the  Arctic  there  are  also  ice  caps, 
resembling  that  of  Greenland,  though  smaller.  There  is  evidence 
that  ice  sheets  once  spread  completely  over  these  islands. 

Summary.  —  TJiere  is  a  great  ice  sheet  on  the  Antarctic  continent, 
and  smaller  sheets  on  some  of  the  larger  islands  of  the  Arctic. 

105.  Formation  of  Icebergs. — When  a  glacier  enters  the  sea  the 
water  buoys  the  ice  up,  causing  great  masses  to  break  off,  forming 
icebergs  (Figs.  265,  267,  268,  339).  Other  masses  are  broken 
away  by  undercutting  along  the  water's  edge.     As  the  icebergs 


146  NE^V  PHYSICAL   GEOGRAPHY. 

drift  slowly  away,  they  melt,  strewing  rock  fragments  along  the 
sea  bottom.  They  often  run  aground  (Fig.  267),  pushing  and 
grinding  the  layers  of  sediment  on  the  bottom. 

It  is  fortunate  that  the  icebergs  drift  aivay  from  the  glacier, 
otherwise  the  fiords  would  soon  become  choked  with  berg  ice. 
They  float  away  in  an  outward  current  of  water  caused  by  winds 
from  the  ice  sheet  and  by  fresh  water  from  the  melting  ice. 

Summary.  —  Icebergs  are  discharged  (1)  by  imdercuttwg  cdong  the 
loater^s  edge,  a)id  (2)  by  buoying  up  of  ice  as  it  advances  into  the  sea. 

106.  Former  Ice  Sheets  in  Europe  and  America.  — There  is 
good  evidence  that,  not  many  thousand  years  ago,  a  great 
ice  sheet  spread  over  northeastern  America  (Fig.  270),  and 
another  over  northwestern  Europe.  Scandinavia,  Denmark, 
northern  Germany,  northwestern  Russia,  and  all  of  the 
British  Isles,  excepting  southern  Enorland,  were  then  cov- 
ered by  ice.  Canada  east  of  the  Rocky  Mountains,  New 
England,  northern  New  Jersey,  nearly  all  of  New  York, 
northern  Pennsylvania,  much  of  Ohio,  and  the  states  farther 
west  and  northwest,  as  far  as  Montana,  were  also  ice-covered. 
These  ice  sheets,  which  were  quite  like  those  now  covering 
Greenland  and  the  Antarctic  continent,  have  been  called 
continental  glaciers.  - 

The  proofs  of  these  former  ice  sheets  are  of  the  same  kind 
as  those  of  former  greater  extension  of  valley  glaciers  (p.  141) 
and  of  the  Greenland  glacier  (p.  145).  These  proofs  include 
glacial  scratches  (Figs.  289,  291),  glacial  pot  holes,  and  er- 
ratic bowlders  (Fig.  285).  The  scratches  point  toward  the 
north,  and  many  of  the  bowlders  can  be  traced  to  a  northern 
source,  some  in  the  United  States  having  come  from  Canada. 
There  is  also  evidence  of  ice  erosion  and  valley  deepening; 
and  there  are  lakes  in  rock  basins  that  the  ice  scoured  out 
(p.  158).  Where  the  ice  stood,  the  land  is  covered  by  a  sheet 
of  ground  moraine,  and  there  are  bands  of  terminal  moraine 
(Fig.  274),  with  wash  deposits  in  front  (Fig.  275).  Tliese  gla- 
cial deposits  were  called  drift,  because  they  were  thought  to 


GLACIERS  AND   THE  GLACIAL  PERIOD.  147 

have  been  brought,  or  drifted,  by  great  floods  of  water  ;  and 
the  term  glacial  drift  is  still  applied  to  them. 

Louis  Agassiz,  in  the  middle  of  the  last  century,  first  proposed 
the  glacial  theory  to  account  for  this  drift.  Being  a  Swiss,  he  had 
studied  glaciers  in  Switzerland,  and  had  seen  the  clear  evidence 
(p.  141)  that  Alpine  glaciers  were  formerly  more  extensive.  He 
saw  that  the  same  evidence  was  present  in  the  British  Isles  and 
in  America,  and  proposed  the  theory  that  there  had  been  a  Glacial 
Period.  This  at  first  m.et  a  storm  of  opposition,  but  is  now 
accepted  by  every  one  who  has  studied  the  question  intelligently. 

Summary.  —  Strim,  erratics,  evidences  of  erosioyi,  moraines,  etc., 
jirove  that  great  continental  glaciers,  or  ice  sheets,  formerly  covered 
northeastern  America  and  northwestern  Euroj^e.  Louis  Agassiz 
proposed  the  noio  accepted  explanation  of  the  Glacial  Period. 

107.  Cause  of  the  Glacial  Period.  —  Why  there  should  have  been 
a  glacial  climate  in  temperate  latitudes  is  not  positively  known. 
At  present  the  climate  of  Labrador,  Scandinavia,  and  other  centers 
from  which  the  ice  spread,  is  very  cold  ;  and,  if  they  were  elevated 
se\^eral  hundred  feet,  great  ice  caps  might  slowly  gather  on  them 
and  spread  out  into  lower  and  warmer  regions.  Before  the  Gla- 
cial Period  these  lands  actually  were  higher  than  now,  and  one 
theory  is  that  this  former  elevation  caused  great  ice  sheets  to  form 
and  move  down  into  the  United  States  and  Europe.  In  the 
United  States  an  ice  sheet  from  Labrador  joined  forces  with  ice 
sheets  from  the  Adirondack  and  New  England  mountains,  and 
spread  over  hill  and  valley,  advancing  slowly  and  irresistibly,  as 
the  ice  sheet  of  Greenland  does.  It  advanced  southward  to  a 
zone  where  melting  became  so  great  that  it  could  go  no  farther. 

After  many  thousand  years  the  climate  gradually  changed, 
perhaps  because  the  land  was  lowered.  Then  the  ice  front 
slowly  melted  back,  or  "  retreated."  We  do  not  know  how  long 
ago  the  ice  melted  away,  but  there  is  evidence  pointing  to  from 
5000  to  10,000  years  (p.  333).  The  time  since  the  ice  left  is  so 
short,  however,  that  the  drift  deposits  are  still  quite  fresh ;  and 
even  delicate  striae  remain  (Fig.  289)  wherever  protected  by  a 
thin  coating  of  soil  (p.  41). 


148 


NEW  PHYSICAL   GEOGRAPHY, 


Summary.  —  One  theory  for  the  Glacial  Period  is  that  when  the 
land  was  higher  in  Labrador  ayid  /Scandinavia,  ice  caps  formed  and 
spread  out  in  all  directions,  and,  after  many  thousand  years,  when 
the  land  was  lowered,  melted  away. 

108.  Terminal  Moraines.  —  While  the  ice  sheet  was  melt- 
ing back  there  were  periods  when  it  halted  for  a  time 
and  built  terminal  moraines  (Fig.  274).       These  bands  of 

moraine,  which 


K-XvX-rl  Drift'  Bearing  Area       ^Striae    %,-,;y"  Moraine 


"iiv  Glacial  MovemenU 
(Generalized) 


resemble  those 
now  forming  at 
the  margin  of  gla- 
ciers,  may  be 
easily  traced. 
They  consist  of 
irregular,  hum- 
mocky  hills,  vary- 
ing from  a  few 
feet  to  100  or  200 
feet  in  height, 
and  inclosing 
many  basins,  or 
kettles,  often  oc- 
cupied by  ponds. 
The  moraines  are  made  partly  of  till,  and  partly  of  stratified 
drift  deposited  by  water  from  the  melting  ice. 

Ice  tongues,  or  lobes,  extended  farther  in  the  valleys  than  on 
the  hills,  and  on  this  account  the  moraines  bend  southward  in  the 
valleys,  forming  looped  or  lobate  moraines  (Figs.  269,  273).  Ter- 
minal moraines  were  built  at  each  halt  of  the  receding  ice  sheet, 
and  they  are  called  moraines  of  recession  (Fig.  273) . 

Summary.  —  At  each  halt  of  the  receding  ice  sheet  a  terminal 
moraine  was  built  with  lobes  extending  doimi  the  valleys.  These 
moraines  are  low,  hummocky  hills,  with  inclosed  basins,  or  kettles^ 
often  occupied  by  ponds. 


Fig.  269.  —  Lobate  moraines  in  the  Central  States, 
showing  the  influence  of  the  Great  Lakes  valleys 
in  causing  the  ice  tongues  to  extend  farther  south. 


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Fig.  271.  —  Edge  of  the  Greenland  ice  sheet  on  the  land  (near  Fig.  264).  The 
dai'k  layers  of  ice  are  due  to  rock  fratrinents.  and  the  ridge  in  the  fore- 
ground is  a  moraine  built  by  the  falling  of  these  from  the  ice  margin. 


Fio.  272.  —  A  stream  extending  from  a  Greenland  ice  tongue  and  flowing  in 
braided  course  over  a  wash  plain  which  it  is  building  up  (see  also  Fig.  2(36). 


PLEISTOCENE  GEOLOGY 

OF 

WESTERN  NEW  YORK 

H.UFaiivhild 


Fig.  2T>i. — The  lobate  moraines  of  recession  in  western  New  York.  The  outer- 
most terminal  moraine  is  the  one  that  bends  up  from  Pennsylvania  to  Sala- 
manca and  Olean.  Also  location  of  drumlins,  and  of  shore  lines  of  glacial 
lakes.  The  heavy  line  is  the  divide.  The  lakes  have  all  been  caused  by 
glacial  action. 


Fig.  274.  —  Photograph  in  the  terminal  moraine  near  Ithaca,  N.Y.    Notice  how 
laummocky  the  surface  is;  this  is  characteristic  o^  moraines. 


Fig.  275.  —  A  wash  plain  near  Fig.  274,  deposited  by  a  stream  flowing  from  the 
glacier  when  the  moraine  was  being  built.    Compare  Figs.  251,  266,  and  272. 


Fig.  276.  —  A  kame  near  Fig.  275.  It  is  made  entirely  of  strtltified  gravel,  and 
in  the  center,  just  above  the  tree  to  the  right  of  the  horse,  has  a  very  deep 
kettle  hole  that  looks  like  a  crater. 


GLACIERS  AND  THE  GLACIAL  PERIOD.  149 

109.  Stratified  Drift.  —  Water  issuing  from  the  melting 
glacier  built  several  classes  of  deposits.  All  these  are  strati- 
lied,  because  water  assorts  rock  fragments  (p.  32).  These 
stratified  deposits  are  called  stratified  drift.  Of  these  the 
most  extensive  are  the  wash  plains  (Fig.  275),  which  re- 
semble those  now  forming  in  the  Swiss  valleys  (p.  139). 
Many  valleys  in  eastern  America  are  filled  to  a  depth  of 
from  100  to  300  feet  with  these  level,  gravelly  j)lains,  built 
by  ancient  glacial  streams.  Wherever  the  ice  front  rested  on 
fairly  level  land  the  glacial  streams  built  a  series  of  low,  flat 
alluvial  fans.  The  plains  on  the  south  side  of  Long  Island 
are  of  this  origin. 

At  and  under  the  ice  front  the  water  built  irregular,  hummocky 
hills  of  gravel,  called  kames  (Fig.  276),  in  which  deep  basins, 
or  kettles,  are  often  found.  Some  of  the  kames  were  appar- 
ently made  by  streams,  bearing  much  gravel,  which  tumbled  to 
the  bottom  of  the  glacier  through  crevasses.  This  gravel  occa- 
sionally covered  blocks  of  ice  which,  on  melting,  allowed  the 
gravel  to  settle,  forming  the  kettle  holes. 

Long,  narrow  ridges  of  gravel,  sometimes  miles  in  length,  and 
with  an  irregular,  serpentine  course,  are  called  esJcers  (Fig.  282). 
These  are  the  gravel  beds  of  streams  that  flowed  in  tunnels  or 
gorges  in  the  ice,  usually  at  the  bottom.  Where  these  streams 
emerged  from  their  ice  tunnels  they  built  wash  plains ;  or,  if  the 
end  was  in  small,  ice-dammed  lakes,  they  built  deltas.  These 
level-topped  deltas  are  called  sand  plains. 

Summary.  —  Water  fro7n  the  melting  ice  made  stratified  deposits  : 
kames  ivJiere  streams  tumbled  to  the  base  of  the  ice  ;  eskers  where 
they  flowed  in  ice  tuimels  ;  ivash  plains  where  they  emerged  upon  the 
land  ;  and  sand  plains  in  small,  ice-damnhed  lakes. 

110.  Ice-dammed  Lakes.  —  In  some  places  the  ice  front 
stood  in  large  lakes  (Figs.  278,  279),  formed  where  north- 
flowing  streams  were  dammed  by  the  ice.  Clay  and  gravel 
deposits  were  made  in  these,  and  along  their  shores  deltas 
and  beaches  were  built. 


150 


NJiJW  PHYSICAL   GEOGRAPHY, 


One  of  tliesc  large  lakes  was  formed  in  the  valley  of  the 
Red  River  of  the  North  (p.  78).  Other  north-flowing 
streams  were  dammed  by  the  ice,  some  of  the  valleys  having 
small,  others  large,  glacial  lakes.  The  case  of  the  Great 
Lakes  is  especially  interesting.  At  first  a  few  small  lakes 
were  formed,  one  outflowing  past  Chicago,  one  past  Duluth, 
and  one  past  Fort  Wayne,  Ind.  (Fig.  280).  As  the  ice 
melted  back  these  grew  larger,  uniting  and  outflowing  past 

Chicago  (Fig. 
280).  Then  an 
enormous  volume 
of  water,  compa- 
rable to  Niagara, 
escaped  into  the 
Illinois  River. 
The  small  lake 
harbor  around 
which  Chicago 
has  grown  up  was 
scoured  out  by 
this  outflow.  As 
the  ice  continued 
to  melt  back,  a  still  lower  outlet  was  opened  eastward  through 
the  Mohawk  valley  (Figs.  277,  280),  the  Chicago  outlet  was 
abandoned,  and  for  a  while  the  glacial  lakes  outflowed  into 
the  Hudson  past  Little  Falls,  N.Y.  Finally,  when  the  ice 
disappeared  from  the  St.  Lawrence  valley,  the  present  course 
was  established. 

The  beaches  that  were  formed  at  the  levels  of  the  different 
outlets  of  these  various  lakes  may  still  be  clearly  seen.  For 
example,  the  beach  ridge  from  Syracuse  to  Lewiston  (Fig. 
273),  on  which  the  "  ridge  road  "  is  built,  was  recognized  as 
a  beach  by  the  early  explorers.  The  fine-grained  clay  that 
was  deposited  on  these  lake  bottoms  makes  a  level,  fertile 
soil.     Consequently,  the  region  between  the  elevated  beaches 


Fig.  277.  —  The  Ontario  region  during  the  stage  of 
outflow  through  the  Mohawk  (Fig.  280  ;  see  also 
Fig.  273). 


Fig.  278.  —  Diagram  of  an  ice  sheet  ou  an  irregular  land,  damming  up  a  series  of 
lakes  along  its  margin.     Describe  what  you  see. 


Fig.  279. — The  same  as  Fig.  278  with  the  ice  melted  back  somewhat,  uncover- 
ing a  valley  which  it  had  crossed.  A  moraine  marks  the  former  position  of 
the  ice  front  in  the  glacial  lake.    Describe  what  you  see  in  this. 


_  -tJ    c 

C     O     4) 

c3   S  A 


GLACIERS  AND    THE  GLACIAL   PERIOD. 


151 


and  the  present  lake  shores  is  the  seat  of  prosperous  farms, 
orchards,  and  vineyards. 

The  beaches  are  not  horizontal,  but  rise  toward  the  north- 
east at  the  rate  of  about  three  to  five  feet  a  mile ;  and  this  is 
taken  as  proof  that  the  land  has  been  tilted  since  they  were 
formed.  As  a  result  of  this  tilting,  the  lakes  have  changed 
from  one  outlet  to  another  (Figs.  280  and  281). 

Uplift  of  the  land  is  still  in  progress  at  a  very  slow  rate,  and 
if  it  continues,  the  upper  Great  Lakes  will  eventually  abandon 
the  Detroit  channel 
and  once  more  out- 
flow past  Chicago. 
At  the  present  rate 
of  tilting  the  water 
will  begin  to  spill 
over  the  Chicago 
rim  in  500  or  600 
vears ;  and  in  3500 
years  Niagara  will 
be  changed  to  a 
very    small    stream. 


Summary.  —  As    Fig.  281.  — After  the  ice  had  entirely  left  the  St.  Law- 


the  ice  ivas  melting 
from  the  land  it 
dammed  north-floio- 
iiKj  streams,  causing 
te  mpo  rary     glacial 


rence  valley,  the  land  in  the  north  was  so  low  that 
the  sea  (shaded)  entered  the  Champlain  and  On- 
tario basins,  and  the  upper  Great  Lakes  outflowed 
through  the  Ottawa  River.  Then  Niagara  carried 
the  water  only  of  Lake  Erie.  As  the  land  in  the 
north  rose,  the  upper  lakes  were  tilted  until  they 
finally  overflowed  past  Detroit. 


lakes  ichich  disap- 
peared ivheii  the  ice  dam  melted  away.  Lakes  of  this  soi^t  were 
formed  in  the  valleys  of  the  Great  Lakes,  shifting  their  outlets  as 
lower  ones  were  uncovered  by  ice  melting,  or  made  j^ossible  by  land 
tilting.      The  tilting  of  the  land  is  still  in  progress. 

111.    Loess. — In  central  United  States  there  is  a  sheet  of  fine- 
textured  clay  known  as  loess,  a  German  name  for  a  similar  deposit 
in  that  country.     Some  of   the  loess  was  evidently  drifted  by 
vinds,  and  some  of  it  was  brought  from  the  ice  front  in  slov.dy 


152  NEW  PHYSICAL   GEOGRAPHY, 

moving  sheets  of  water.     In  China  there  is  an  extensive  deposit 
of  loess  brought  by  the  wind. 

Summary.  —  Loess  is  a  fine-textured  clay,  in  some  cases  ivind 
deposited,  in  others  brought  by  sloidy  moviyig  sheets  of  icater, 

112.  The  Till  Sheet.  —  The  principal  soil  of  a  glaciated 
country  is  till  or  bowlder  clay^  which  occupies  the  region  be- 
tween the  moraines,  wherever  the  surface  is  not  covered  by 
stratified  drift.  Till  is  a  compact  clay,  usually  unstratified, 
with  bowlders  and  pebbles  mixed  through  it  (Fig.  283).  It 
is  the  ground  moraine  left  when  the  ice  melted. 

The  till  sheet  varies  greatly  in  thickness,  being  usually 
thin  where  the  rock  is  hard,  and  thick  where  it  is  soft  and 
easily  ground  up.  In  Labrador,  and  in  hilly  New  England, 
there  are  large  areas  with  little  or  no  till ;  but  in  the  Mis- 
sissippi valley,  where  the  land  is  more  level  and  the  rock 
softer,  the  till  sheet  is  sometimes  100  or  200  feet  thick. 

There  is  also  much  difference  in  composition.  In  some 
places  it  is  made  of  clay  with  only  occasional  bowlders ;  in 
others  it  is  so  full  of  bowlders  that  farming  is  almost  impos- 
sible (Fig.  284).  An  abundance  of  bowlders  is  likely  to  be 
found  just  south  of  mountain  areas  of  hard  rock,  as  in  New 
England,  and  south  of  the  Adirondacks.  They  sometimes 
form  trails,  or  hoivlder  trains^  from  the  place  of  origin,  grow- 
ing less  common  and  smaller  as  the  distance  from  the  source 
increases,  because  of  the  erosion  to  which  they  have  been  sub- 
jected. In  ceritral  New  York,  where  the  bowlders  are  largely 
hard  rock  from  the  north,  farmers  call  them  "hardheads." 

Summary.  —  Till  or  bowlder  clay,  the  most  imdespread  glacial 
deposit,  is  the  ground  moraiiie.  It  is  a  sheet  of  mixed  clay  ant 
bowlders  varying  in  thickness  and  in  the  proportion  of  bowlders. 

113.  Drumlins.  —  In  many  sections  the  till  sheet  is  smooth  and 
regular,  covering  the  surface  to  a. fairly  even  depth;  in  other 
places  it  is  ridged  and  irregular.  One  peculiar  irregularity  of  till 
is  the  drumlin  (Figs.  286-288).     Drumlins  vary  from  100  feet  to 


•1- 


l-L 


Fio.  282.— An  esker  ridge  near  Ithaca,  N.  Y, 
This  is  a  stream  deposit  made  in  a  tun- 
nel underneath  the  glacier. 


Fig.  283.— a  section  in  till  in  which 
there  are  not  many  bowlders. 


Fig.  284.— a  bowlder-strewn,  glacial  soil  in  Maine. 


Fig.  285. — Large  glacial  bowlders  brought  b^  the  ice, 


Fig.  28b.  —  A  drumlin  at  Ipswich,  Mass. 


Fig.  287.  —  A  drumliu  nortl)  of  Auburn,  N.Y. 


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Fig.  289.  —  The  eud  of  the  hammer  handle  rests  on  a  glacial  scratcl' 

on  a  ledge  of  shale  rock. 


Fig.  290.  —  A  pebble  with  glacial  Fi(..  291. — A  i)(4)l)le  with  glacial   scratches; 
scratches;    taken    from    the  taken  from  a  till  bed  at  Ithaca,  N.  Y. 

Greenland  ice  sheet  at  the 
place  shown  in  Fig.  271 . 


GLACIERS  AND   THE  GLACIAL   PERIOD.  153 

a  mile  or  more  in  length,  and  from  20  to  100  or  200  feet  in  height. 
Some  are  long  and  ridge-like ;  some  short  and  lumpy ;  but  the 
most  typical  drumlins  are  oval,  having  the  shape  of  a  half-sub- 
merged egg  (Fig.  286),  with  the  long  direction  parallel  to  the  water 
surface.     They  are  masses  of  till  ridged  up  under  the  ice. 

Drumlins  usually  occur  in  clusters.  There  is  one  group  in  Wis- 
consin, near  Madison  (Fig.  288) ;  another  in  central  New  York 
between  Rochester  and  Syracuse,  and  northward  to  Lake  Ontario 
(Fig.  273,  287)  ;  another  in  the  Connecticut  valley ;  another  in 
and  near  Boston  (Fig.  286).  Boston  is  built  on  drumlins,  of  which 
Bunker  Hill  is  one. 

Summary.  — Elongated  ridges  of  till,  usually  in  clusters,  are  called 
drumlins.  Tliey  vary  greatly  in  shape  and  size,  the  most  perfect 
having  the  oval  shape  of  a  half  egg. 

114.  Glacial  Erosion.  —  In  a  glaciated  country  wherever 
the  rock  is  uncovered,  its  surface  is  likely  to  be  polished, 
scratched,  and  grooved  (Fig.  289).  In  eastern  United  States 
the  striae  point  toward  Labrador.  Strise  and  erratics  found 
on  high  mountains  prove  that  the  ice  was  thick  enough  to 
override  the  tops  of  mountains  even  a  mile  in  height. 

The  northern  slopes  of  hills  and  mountains  over  which  the 
ice  moved  are  often  rounded  by  ice  erosion  ;  and  ledges  have 
the  smoothed  and  rounded  form  of  the  roclies  moutonnees 
fp.  142).  Pebbles  and  bowlders  in  the  till  are  also  smoothed 
and  scratched  (Fig.  291).  It  is  evident  that  much  work  of 
erosion  was  done  as  the  ice  sheet  moved  onward,  pressing 
down  with  enormous  weight,  and  dragging  its  rock  load  over 
the  land.     It  acted  like  a  great  rasp  or  sheet  of  sandpaper. 

By  this  erosion  some  rock  was  removed  from  the  hills,  but  more 
was  worn  from  those  valleys  along  which  the  ice  moved  freely. 
In  this  way  many  north-south  valleys  were  so  deepened  that  their 
tributaries  now  enter  through  hanging  valleys  (Fig.  293) ;  and  the 
same  is  true  of  bays  and  fiords  on  the  coasts  of  Maine,  Labrador, 
Alaska,  and  Norway.  By  such  erosion  the  valleys  of  the  larger 
Finger  Lakes   of  central  New  York  (Cayuga  and  Seneca)  were 


154 


NEW  PHYSICAL   GEOGRAPHY, 


deepened ;  and  part  of  the  depth  of  Lake  Ontario,  and  others  of 
the  Great  Lakes,  is  also  due  to  ice  erosion.  During  this  erosion, 
rock  basins,  in  which  lakes  and  ponds  now  stand,  were  scoured 
out.     Thus  the  land  surface  was  decidedly  modified  by  erosion. 

Summary.  —  That  the  ice  sheet  did  much  erosion y  is  proved  by 
striated  pebbles,  bowlders,  and  ledges  ;  by  rounded  north  slopes  ;  by 
roches  moutonyiees  ;  by  hanging  valleys  ;  and  by  rock  basins.  The 
ice  sheet  acted  like  a  great  rasp,  planing  doivn  the  surface,  especially 
in  valleys  through  luhich  it  freely  moved. 


Fig.  292.  —  To  illustrate  the  effect  of  glacial  deposits  (dotted)  in  leveling  a  hilly 
country  by  filling  the  valleys,  as  in  the  prairie  region  of  the  Central  States. 

115.  Effects  of  the  Ice  Sheet.  — In  some  places  the  surface 
was  roughened  by  the  deposit  of  drumlins,  eskers,  kames,  and 
moraines.  Elsewhere  the  drift  has  smoothed  the  surface  by 
making  thicker  deposits  in  the  valleys  than  on  the  hills. 
This  smoothing  reaches  its  extreme  in  the  prairie  region  of 
the  Central  States,  where,  in  some  cases,  drift  in  the  val- 
leys has  a  depth  of  500  feet.  Tlie  level  surface  and  fertile 
soil  of  the  prairie  are  therefore  due  to  the  glacier  (Fig.  292). 

Throughout  the  glacial  belt  the  drift  soil  shows  many  vari- 
ations; for  example,  stony,  clayey,  sandy,  gravelley,  level, 
irregular.  On  a  single  farm  there  may  be  several  kinds 
of  soil.  Sometimes  this  is  better  than  the  soil  of  rock  decay 
that  existed  before  the  ice  sheet  came  ;  in  other  cases  a  barren, 
sandy,  gravelly,  or  bowldery  soil  (Fig.  284)  has  been  left  in 


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GLACIERS  AND   THE  GLACIAL  PERIOD. 


155 


PROBABLE 

PREGLACIAL  DRAINAGF 

OF  THE 

I'PPER  OHIO  REGION. 


place  of  a  fertile  residual  soil.  Usually  the  glacial  soil  is  a 
strong  one,  because  it  consists  of  ground-up  rock  fragments, 
which  are  slowly  decaying  and  releasing  plant  food. 

The  sheet  of  drift  has  turned  many  streams  aside,  caus- 
ing them  to  cut  new  valleys  for  a  part  of  their  course.  In 
these  the  streams  have  often 
reached  the  rock  and  cut  post- 
glacial gorges,  in  which  there 
are  rapids  and  falls  (Figs. 
60,  67,  71,  75).  There  are 
thousands  of  instances  of  this, 
and  many  of  the  falls  are  of 
great  value  for  water  power; 
for  instance,  the  falls  in  the 
Mississippi  at  Minneapolis, 
Niagara,  the  falls  at  Roches- 
ter, and  the  rapids  in  the 
.Merrimac  where  Manchester, 
Lawrence,  and  Lowell  are 
situated.  South  of  the  gla- 
cial belt  there  are  few  places 
where  there  is  water  power ; 
but  in  New  England,  New 
York,  and  other  states  in  the 
glacial  belt,  it  is  this  water 
power  that  has  given  rise  to 
so  much  manufacturing. 


Fig.  295.  —  Compare  this  map  with  one 
of  the  present  drainage.  For  pur- 
pose of  comparison,  make  a  sketch 
map  of  the  present  drainage  from  a 
geography  map. 


In  some  cases  streams  have  been  turned  into  other  river  sys- 
tems. Before  the  glacial  period  the  upper  Ohio,  above  Wheeling 
(Fig.  295),  flowed  into  Lake  Erie  valley  through  the  Grand  River ; 
and  the  Allegheny  is  made  by  the  union  of  two  streams,  one  of 
which  entered  the  Lake  Erie  valley  west  of  Erie,  Pa.,  the  other 
east  of  Dunkirk,  N.Y.  The  present  St.  Lawrence  system  has  also 
been  made  by  the  union  of  several  independent  parts. 

Could  we  restore  the  pre-glacial  drainage  of  the  United  States, 


156  J^EW  PHYSICAL   GEOGRAPHY, 

it  would,  in  thousands  of  cases,  be  found  different  from  the  pres- 
ent. Some  of  these  changes  have  been  of  great  importance ;  for 
example,  how  different  would  have  been  the  history  of  Pittsburg 
if  there  had  been  a  waterway  to  the  north  (Fig.  295)  instead  of  to 
the  southwest !  How  different  would  have  been  the  history  of 
Cincinnati  if  the  Ohio  flowed  past  it  as  a  small  stream  without  its 
great  tributaries,  the  Allegheny  and  Monongahela !  And  what  a 
contrast  there  would  be  where  Buffalo  and  the  other  lake  cities 
stand  if  glacial  changes  had  not  united  streams  and  caused  lake? 
in  the  valleys  of  the  St.  Lawrence  system ! 

Of  the  tens  of  thousands  of  lakes  in  the  glacial  region,  the 
great  majority  are  due  to  some  interference  of  drift  deposits 
with  drainage  (Figs.  297-300).  This  is  true  of  the  small 
ponds  and  lakes,  of  which  there  are  said  to  be  10,000  in 
Minnesota  alone ;  and  it  is  true  of  the  many  large  lakes. 
Even  the  basins  of  the  Great  Lakes,  caused  in  part  by  glacial 
erosion  and  changes  in  level  of  the  land,  owe  a  portion  of 
their  depth  to  dams  of  glacial  drift.  What  an  important 
difference  it  would  make  in  the  cities  and  industries  of  north- 
ern United  States  if  glacial  action  had  not  caused  the  lakes 
which  dot  the  surface! 

Summary.  —  TJie  ice  sheet  caused  many  changes,  making  some 
regions  rougher  than  before,  others  smoother ;  it  chayiged  the  soil, 
causing  it  to  differ  greatly  from  place  to  place  ;  by  turniiig  streams 
aside,  it  led  to  the  formation  of  many  gorges  and  waterfalls  ;  it  has 
even  turned  streams  into  other  systems  ;  and  it  has  made  thousands 
of  lakes,  great  and  small. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  —  99.  Valley  Glaciers. —  (a)  Formation:  snow 
field ;  movement  of  snow  ;  neve ;  formation  of  ice ;  extension  of  ice 
tongue,  (h)  Movement:  nature;  rate;  glacial  erosion .  (c)  Moraines: 
lateral ;  medial ;  crevasses;  ice  falls;  movement  of  materials  to  bottom; 
ground  moraine ;  terminal  moraine,  (c?)  Wash  deposits :  source  of 
water ;  of  sediment ;  rock  flour ;  nature  of  deposit. 

100.  Glaciers  of  Alaska. —  (a)  Muir;  tributaries;  front;  withdrawal. 
(h)  Malaspina:  form;  size;  movement;  surface  condition. 


GLACIERS  AND   THE  GLACIAL  PERIOD.  157 

101.  Distribution  of  Valley  Glaciers.  —  Europe;  North  America, — 
Mexico,  United  States,  Canada,  Alaska ;  Arctic ;  southern  hemisphere. 

102.  Former  Extension  of  Valley  Glaciers.  —  (a)  Instances,  (b)  Evi- 
dence: erratics;  striae;  moraines;  till;  wash  deposits,  (c)  Ice  erosion : 
roches  moutonn^es  ;  rock  basins;  cirques;  hanging  valleys. 

103.  The  Greenland  Ice  Sheet.  —  (a)  General  condition  :  topography ; 
coast ;  valley  glaciers  ;  area  of  ice ;  meaning  of  ice  sheet.  (6)  The  ice 
sheet :  interior  condition ;  outward  motion ;  nunataks ;  valley  tongues  ; 
size;  movement;  icebergs,  (c)  Rock  materials:  on  the  surface;  at  the 
base ;  erosion  ;  deposits  at  margin,     (d)  Former  extension. 

104.  Other  Ice  Sheets.  —  Antarctic  ;  islands  of  Arctic. 

105.  Formation  of  Icebergs.  —  Causes  ;  effects ;  outward  movement. 

106.  Former  Ice  Sheets  in  Europe  and  America.  —  (a)  Extent :  Euroj)e ; 
America;  continental  glaciers,  ^(b)  Proofs:  striae;  erratics;  ice  ero- 
sion ;  glacial  deposits ;  glacial  drift,     (c)   Agassiz's  explanation. 

107.  Cause  of  the  Glacial  Period.  —  Land  formerly  higher;  probable 
result;  retreat  of  ice ;  time  since  ice  withdrawal. 

108.  Terminal  Moraines.  —  Cause  ;  form,  size,  kettles ;  composition ; 
lobate  moraines;  moraines  of  recession. 

109.  Stratified  Drift.  —  Nature  of  stratified  drift;  wash  plains; 
kames;  kettles;  eskers;  sand  plains. 

110.  Ice-dammed  Lakes.  —  Cause ;  Great  Lakes,  —  early  stages,  changes 
in  outflow,  beaches,  lake  clays;  changes  of  level,  —  evidence,  effect  on 
outflow,  present  changes. 

IIL   Loess.  —  Nature;  occurrence;  cause. 

112.  The  Till  Sheet.  —  Distribution  ;  nature  of  material;  variation  in 
thickness;  variation  in  bowlders;  reason  for  variation;  bowlder  trains. 

113.  Drumlins.  —  Size;  shape;  cause;  occurrence. 

114.  Glacial  Erosion.  —  Striae;  north  slopes;  roches  moutonn^es; 
scratched  pebbles ;  nature  of  the  ice  erosion  ;  effect  in  valleys ;  illustra- 
tions ;  rock  basins. 

115.  Effects  of  the  Ice  Sheet. —  (a)  On  the  land  surface  :  irregular  sur- 
faces ;  smooth  surfaces;  prairies,  (b)  On  soil :  differences;  strength 
of  glacial  soils,  (c)  On  streams:  formation  of  gorges  and  falls;  in- 
stances; effect  on  manufacturing  ;  complete  turning  aside  of  streams ;  im- 
portance of  this,  (d)  On  lakes:  cause;  numbers;  Great  Lakes;  importance. 

Questions.  —99.  What  is  the  snow  field?  What  is  the  nature  and 
origin  of  the  n6v6  ?  What  is  a  valley  glacier  ?  Why  does  it  extend  down 
the  valley?  How  does  the  ice  move  ?  What  is  happening  at  its  bottom? 
What  are  lateral  moraines  ?  Medial  moraines  ?  Crevasses  ?  Ice  falls  ? 
What  descends  through  the  crevasses?  What  is  the  ground  moraine? 
Terminal  moraine  ?     Account  for  the  wa§h  deposits. 


158  NEW  PHYSICAL   GEOGRAPHY, 

100.  Describe  the  Muir  glacier.     The  Malaspina  glacier. 

101.  Where  are  the  glaciers  found ?     In  what  zones? 

102.  Where  did  valley  glaciers  formerly  exist  ?  What  are  erratics  ? 
What  is  till?  Why  is  it  nnstratified?  What  work  of  erosion  did 
ancient  glaciers  perform?  What  are  roches  moutonn^es?  Rock  basins? 
Hanging  valleys  ?     State  the  evidences  of  former  valley  glaciers. 

103.  What  is  the  condition  of  Greenland?  What  is  an  ice  sheet? 
What  is  the  condition  in  the  interior?  How  does  the  ice  sheet  move? 
What  is  the  condition  at  its  margin?  How  are  rock  materials  carried? 
What  deposits  are  being  made  ?     State  the  evidence  of  former  extension. 

101.   AVhere  else  are  ice  sheets  found  ? 

105.  What  are  the  causes  for  icebergs?     Why  do  they  drift  away? 

106.  Where  were  there  former  great  ice  sheets?  What  evidence  is 
there  of  former  glaciation  ?  Why  are  the  deposits  called  glacial  drift  ? 
Who  proposed  the  theory  of  the  Glacial  Period  ?     Why  ? 

107.  What  is  the  most  probable  explanation  of  the  glacial  period? 
How  did  the  ice  advance  ?     Why  did  it  retreat  ? 

108.  What  are  the  characteristics  of  terminal  moraines?  What  are 
lobate  moraines  ?     Moraines  of  recession  ? 

109.  What  is  the  cause  of  stratified  drift?  What  are  the  following- 
wash  plains,  kames,  kettles,  eskers,  sand  plains? 

110.  What  changes  occurred  as  the  ice  melted  from  the  Great  Lakes? 
AVhat  deposits  were  made  ?  AVhat  evidence  is  there  of  change  in  level  of 
the  land?     State  the  past  and  possible  future  effects. 

111.  What  is  loess?     How  formed?     Where  found? 

112.  What  is  the  principal  soil  of  the  glacial  region?  Where  is  it 
found  ?     How  does  it  vary  ?    Why  ? 

113.  What  are  drumlins ?     How  do  they  vary ?    Where  found? 

114.  What  proofs  of  glacial  erosion  are  there?  What  were  its  effects 
on  the  valleys  ?     Give  illustrations. 

11.5.  What  effects  had  the  ice  sheet  on  surface  features  of  the  land? 
On  soil?  On  stream  courses?  Give  instances  of  streams  turned  into 
other  systems.     What  effect  had  the  ice  on  lakes? 

Suggestions.  —  (1)  Cut  out  a  square  block  of  ice  and  float  it  m 
water.  Measure  it  to.  see  what  proportion  is  above  water.  Place  the 
same  block  in  salt  water  and  measure  the  proportion  above  water.  (2)  In 
a  box,  the  end  of  which  can  be  removed,  place  thin  layers  of  snow  inter- 
spersed with  sheets  of  mixed  gravel,  sand,  and  clay,  placing  a  much  greater 
amount  in  the  part  from  which  the  end  of  the  box  is  to  be  removed. 
Compact  it  as  tightly  as  possible,  then  allow  it  to  freeze.  Remove  tlie 
end  of  the  box,  allow  the  ice  to  melt,  and  watch  ♦^^he  result.  Does 
a  moraiue-bke  accumulation  form  at  the  front?     DiMi^-  the  surface  of 


GLACIERS  AND  THE  GLACIAL  PERIOD.  159 

the  ice  eventually  become  covered  with  sand?  A  large  number  of 
glacial  phenomena  can  be  imitated  by  a  little  ingenuity, —  for  exam- 
ple, cutting  crevasses,  boring  a  tunnel  at  the  bottom  of  the  ice,  and 
sprinkling  the  ice  surface  to  supply  water.  The  stream  that  issues 
from  the  tunnel  may  be  made  to  build  wash  deposits  on  a  moderate 
slope;  or  to  build  sand  plains  in  temporary  lakes  along  the  ice  margin, 
etc.  (3)  Imitate  moraine  topography  by  dumping  small  pailfuls  of 
sand  in  piles  close  together.  (4)  Is  your  home  in  the  glacial  belt?  If 
so,  what  effects  of  the  glacier  can  you  find  in  the  neighborhood,  either 
by  a  study  of  the  typographic  map  or,  better  still,  on  a  field  excursion? 
Is  the  soil  till  or  stratified  drift?  To  answer  this  question  look  for 
cuts  and  study  them  carefully.  If  till,  look  for  scratched  stones.  If 
stratified,  why  are  the  pebbles  rounded  and  the  scratches  gone?  Look 
for  glacial  scratches  on  recently  uncovered  exposures  of  bed  rock. 
What  is  their  direction?  Are  the  bowlders  and  pebbles  all  of  the  same 
kind  as  the  bed  rock?  Do  you  know  if  any  of  them  could  have  come 
from  ledges  in  the  direction  in  which  the  strife  point?  Can  you  find 
moraines,  kames,  eskers,  or  drumlins?  If  so,  study  them, — their  form 
and  the  nature  of  the  material. 

Reference  Books.  —  Russell,  Glaciers  of  Xorlii  America,  Ginn  &  Co., 
Hostou,  1897,  !$1.75;  '1'arr,  Phijsical  Geographij  of  Ne/v  York  State, 
Chapters  IV  and  VIII,  Macmillan  Co.,  X.Y.,  1902,  f$:j.5();  WhiCxHT,  Ice 
Age  in  North  America,  Appleton  &  Co.,  N.Y.,  4tli  ed.,  1902,  $r).()0 ;  Man 
and  the  Glacial  Period,  Appleton  &  Co.,  N.Y.,  1892,  $1.7.5;  Bonney,  Ice 
Work,  Past  and  Present,  Appleton  &  Co.,  N.Y.,  1896.  ^\  50;  Geikie,  The 
Great  Ice  Age,  Appleton  &  Co.,  N.Y.,  3d  ed.,  1891,  !&7.50;  TYNDAi.r,, 
Glaciers  of  the  Alps,  I.,oiigmans,  (jreen  &  Co.,  N.Y.,  1896,  iS2..50;  Sua  leu 
and  Davis, 'V/r/c/er.s,  Houghton,  Mifflin  &  Co.,  Boston,  1881,  flO;  Lubijock, 
The  Scenerij  of  Switzerland,  Macmillan  Co.,  N.Y.,  1898,  |150;  Salls- 
BURY,  Glacial  Geology,  Vol.  V,  1902,  New  Jersey  Geological  Snrvey, 
Trenton,  N.J. ;  Nansen,  First  Crossing  of  Greenland,  Longmans,  (rreen 
&  Co.,  N.Y.,  1892,  $1.25;  Peary,  Northward  over  the  Great  he,  P.  A. 
Stokes,  N.Y.,  1898,  »'$6.50;  Dryer,  Studies  in  Indiana  Geographg,  Inland 
Publishing  Co.,  Terre  Haute,  Ind.,  1897,  $1.25.  U.  S.  Geological  Survey 
as  follows:  Russell,  Existing  Glaciers  of  United  States,  5th  Annual, 
p.  309;  Mcdaspina  Glacier,  13th  Annual,  p.  7;  Reid,  Muir  Glacier,  16th 
Annual,  p.  421;  Chamberlin,  Terminal  Moraine,  3d  Annual,  p.  295; 
StricB,1th.  Annual,  p.  155;  Leverett,  Illinois  Glacial  Lobe,  Monograph 
XXXVIII;  Glacial  Formations,  etc.,  of  the  Erie  and  Ohio  Basins,  Mono- 
graph XLI ;  Stone,  Glacial  Gravels  of  Maine,  Monograph  XXXIV; 
Cpham,  Glacial  Lake  Agassiz,  Monograph  X.XV, 


CHAPTER  IX 


LAKES  AND  SWAMPS. 


LAKES. 


116.  Origin  of  Lake  Basins.  —  A  lake  is  a  body  of  water 
occupying  a  basin  or  depression  on  the  surface  of  the  land. 
Lakes  form  parts  of  river  systems,  but  their  basins  are  not 

usually  made  by 
the  rivers.  In  their 
work  of  valley  cut- 
ting, rivers  tend  to 
establish  regular 
slopes,  and  they 
are  capable  of  mak- 
ing only  small  ba- 
sins :  for  example, 
pot  holes  (p.  54) 
and  ox-bow  lakes 
(p.  63).  Rivers 
could  not  make 
deep  basins  be- 
cause water  would 
gather  in  them  and 
check  the  current, 
thus  taking  away  its  cutting  power.  The  majority  of  lake 
oasins  are  formed  by  dams  across  stream  valleys. 

Most  of  the  leading  causes  for  lake  basins  have  already  been 
stated.  (See  pages  55,  60,  6.3,  67,  76,  78,  95,  97,  103,  121,  123, 
130,  131,  142,  148,  149,  154,  and  156.)  Make  a  list  of  these 
causes.     From  it  you  will  see  that  there  are  various  reasons  why 

160 


Fig.  296.  — Two  diagrams  of  the  same  valley.  In  the 
lower  figure  a  lake  has  been  formed  by  downfold- 
ing,  or  warping,  of  its  bottom. 


Fig.  29S. — Lake  Cayuga,  central  JNevv  iuiK,  occupying  a  river  val- 
ley broadened  and  deepened  by  glacial  erosion  and  dammed  at 
one  end  by  drift  deposits. 


Fig.   299.  —  Lower  ALLsuuie   lake  in   tlie   .vairondacks,   occupying  a 
mountain  valley  dammed  by  drift. 


LAKES  AND   SWAMPS. 


161 


dams  may  be  made  across  stream  valleys,  changing  them  to  lake 
basins.  By  far  the  most  important  of  these  causes  are  the  glacial 
dams  which  have  so  recently  interfered  with  the  drainage  of  large 
areas  of  Europe  and  America.  Many  lakes,  such  as  the  Great 
Lakes  (p.  156),  are  due  to  a  combination  of  two  or  more  causes. 
There  are  still  other  causes  than  those  already  stated  for  lakes 
and  ponds.  For  example,  beavers  build  dams  of  wood  and  mud 
across*  streams  to  make  swamps  and  ponds  for  their  homes  and 
feeding  grounds.  Man  is  now  one  of  the  most  important  agents 
in  the  making  of  lake  basins.  To  supply  water  for  power,  for  the 
use  of  cities,  and  for  irrigation,  men  are  making  ponds  and  lakes 
in  many  parts  of  the  earth. 

Summary.  —  Lake  basins,  though  parts  of  I'iver  systems,  are  not 
generally  formed  by  the  rivers,  but  by  some  interference  ivith  drainage, 
usually  by  some  kind  of  dam.     Man  is  now  making  ma7iy  lakes. 

117.  Size  and  Form  of  Lakes.  — There  is  every  gradation, 
from  mere  ponds  to  the  largest  of  lakes.  Some  are  very 
shallow ;  others  have  great  depth  ;  in  many  the  bottom  is 
below  sea  level  ;  and  even  the  surface  of  some,  like  Dead 
Sea,  is  below  sea  level.  The  following  tables  give  some 
facts  regarding  the  size  and  depth  of   certain   large  lakes. 

The  Great  Lakes. 


a 

'S 

-a" 

a> 

1  s 

T3  -*j 

5 

c3  3 

and 
water- 
miles. 

3 

J2 

s 

"3 

t 

ST 

>  *^ 

o  <» 

o 

c3  08  =S 

—  a,  3 
_2  is  <^ 

tie 

^,2 

9 

^ 

s  s 

§8 

IE    > 

^-a" 

si  r 

a 
<» 

390 

S 
> 

<! 
TO 

160 

o 

> 
< 

475 

X  c 

cS    CO 

a  ?3 

602 

1^ 

H-5 

S:  s  a* 

Superior     .     .     . 

1,300 

31,200 

1,008 

-406 

2,800 

51,600 

82,800  , 

Michigan   .     .     . 

335 

58 

85 

875 

20,200 

335 

870 

581 

-289 

1,290 

37,700 

60,100 

Huron   .... 

250 

54 

100 

725 

17.400 

210 

702 

581 

-121 

650 

31,700 

55,700 

Erie 

25 

40 

58 

590 

10,000 

70 

204 

573 

369 

130 

22,700 

32,700 

Ontario .... 

180 

40 

68 

600 

7,300 

300 

738 

247 

-491 

410 

21,600 

28,aoo 

M 


162 


NEW  PHYSICAL   GEOGRAPHY, 


Some  of  the  Largest  Lakes  in  the  World. 


Area 

Greatest 

Name. 

(square 

Elevation 

Depth 

miles). 

(feet)  . 

(feet). 

Caspian 

169,000 

-85 

2,400 

Superior 

. 

» 

31,200 

602 

1,008 

Victoria  Nyanza 

» 

• 

30,000 

4,000 

590 

Aral 

26,900 

160 

225 

Huron 

17,400 

581 

702 

Michigan 

20,200 

581 

870 

Nyassa 

14,000 

1,500 

600+ 

Tanganyika 

12,650 

2,800 

2,100 

Baikal  . 

12,500 

1,312 

4,550 

Great  Bear  . 

11,200 

200 

Great  Slave 

« 

10,100 

650r 

Chad    . 

10,000+ 
variable 

8-900 

1-2 

Erie      . 

10,000 

573 

204 

Winnipeg     . 

9,400 

710 

70 

Balkash 

7,800 

780 

:35+ 

Ontario 

7.300 

247 

73S 

The  great  majority  of  lakes  are  longer  in  one  aixection 
than  in  others.  The  explanation  of  this  fact  i.s  that  they 
occupy  parts  of  river  valleys,  and,  therefore,  hav6  a  long  axis 
in  the  direction  of  the  valley.  If  the  water  risen  into  tribu- 
tary valleys,  the  outline  of  the  lake  becomes  irregular,  as  in 
tlie  case  of  Lake  Champlain.  Because  the  basin  which  they 
occupy  is  round,  some  lakes  are  nearly  circular.  This  is 
true,  for  instance,  of  crater  lakes  (Figs.  215,  216,  225),  sink- 
hole lakes  (p.  60),  and  kettle-hole  ponds  (Fig-  294). 

Deltas  built  out  into  lakes  help  to  make  them  irregular ; 
.md,  on  the  projecting  deltas,  towns  and  villages  are  often 
ulaced  (Figs.  107,  297).  Deltas  at  the  head  of  lakes,  where 
the  inlet  streams  enter,  shorten  the  lake. 

On  the  other  hand,  waves  tend  to  straighten  lake  shores 
by  cutting  back  headlands  and  building  beaches,  which  often 
shut  in  small  bays,  transformin>r  them  to  ponds  (Fig.  370). 


Fig.  301.  —  A  map  sliovviug  the  extent  of  ancient  Lake  Bonneville,  as  indicated' 
by  the  beaches  and  other  shore  lines  on  the  surrounding  luouutaiu  slopes. 
The  present  Great  Salt  Lake  is  shown  ocoupying  a  part  of  the  desert  plain  on 
the  sUe  of  this  extiuct  lake. 


LAKES  AND  SWAMPS.  168 

Summary.  —  Lakes  vary  greatly  in  size,  depth,  and  form ;  but 
most  lakes  are  long,  because  they  occupy  parts  of  river  valleys. 
Deltas  on  the  sides  of  lakes  make  them  irregular;  but  ivaves  tend 
to  straighten  the  shores. 

118.  Salt  Lakes.  —  Tlie  largest  lake  in  tlie  world,  the 
Caspian  Sea,  is  salt.  It  receives  an  enormous  inflow  of  fresh 
water  from  the  Volga  and  other  rivers ;  but  in  that  dry 
clima^^\  evaporation  is  so  rapid  that  the  water  does  not  fill 
the  basin  and  overflow.  Its  surface  is  about  85  feet  below 
sea  level. 

Dead  Sea,  whose  surface  is  1300  feet  below  sea  level,  is 
one  of  the  saltest  lakes  in  the  world,  being  nearly  a  quarter 
salt,  although  entered  by  tlie  fresh-water  Jordan. 

Great  Salt  Lake  is  about  one  fifth  sp.lt ;  and  this  amount 
so  increases  the  density  of  the  water  that  a  man  cannot  sink 
in  it.  Where  the  water  has  risen  over  the  low  plain  sur- 
rounding the  lake,  and  evaporated,  the  ground  is  incrusted 
with  salt ;  and,  by  leading  the  water  into  shallow  basins,  and 
allowing  it  to  evaporate,  salt  for  use  is  obtained. 

The  explanation  of  salt  lakes  in  dry  climates  is  as  follows  : 
Streams  carry  salt,  gypsum,  carbonate  of  lime,  and  other 
mineral  substances  in  solution  (p.  51).  Where  lakes  have 
outflows,  these  substances  are  in  part  borne  away  by  the 
outlets ;  but  in  arid  climates  evaporation  is  so  great  that 
the  lakes  cannot  rise  and  overflow  the  rims  of  their  basins. 
Therefore,  while  the  water  is  removed  by  evaporation,  the 
mineral  substances  are  left,  and  the  water  grows  gradually 
Salter.  If  evaporation  continues  long  enough,  there  will  be 
so  much  salt  that  some  of  it  must  be  deposited  on  the  bot- 
tom. Great  Salt  Lake  is  not  yet  salt  enough  for  this ;  but 
carbonate  of  lime  is  being  deposited. 

In  the  Great  Salt  Lake  basin  there  are  wonderfully  perfect 
deltas,  beaches,  and  wave-cut  cliffs  on  the  mountain  sides,  hun- 
dreds of  feet  above  the  valley  bottom.     By  tracing  these  shore 


164  NEW  PHYSICAL  GEOGRAPET. 

lines  it  is  found  that  a  great  fresh-water  lake,  now  named  Lake 
Bonneville  (Fig.  301),  formerly  filled  this  basin,  overflowing  into 
the  Columbia.  Its  area  was  as  great  as  that  of  Lake  Huron, 
and,  on  the  site  of  Salt  Lake  City  (Fig.  133),  the  water  was  over 
1000  feet  deep.  Great  Salt  Lake  is  the  f.hrunken  descendant 
of  Lake  Bonneville,  occupying  a  shallow  depression  on  the  lake- 
bottom  plain.  In  other  arid  regions  there  is  evidence  of  former 
periods  of  greater  moisture. 

Summary.  —  Salt  lakes,  common  in  arid  regions,  are  due  to  the 
fact  that  evaporation  prevents  the  water  from  rising  to  a  point  of 
overflow,  and,  by  removing  the  ivater,  leaves  behind  salt  and  other  dis- 
solved mineral  substances.  Elevated  shore  lines  aroimd  the  basin  of 
Great  Salt  Lake  prove  former  periods  of  greater  moisture, 

119.  Life  History  of  Lakes.  —  Some  lakes  disappear  by 
the  sudden  removal  of  the  dam,  as  in  the  case  of  glacial 
lakes  (p.  149);  others,  like  Lake  Bonneville,  disappear  by 
evaporation.  But  most  lakes  have  a  different  life  history, 
being  destroyed  partly  by  filling,  partly  by  cutting  down  at 
the  outlet.  Cutting  at  the  outlet  is  usually  slight,  because 
the  sediment  has  been  filtered  out  in  the  quiet  lake  water, 
thus  robbing  the  outlet  stream  of  tools  for  erosion.  This 
is  illustrated  by  Niagara  River,  which,  though  emerging 
from  Lake  Erie  with  great  volume,  has  been  able  to  do 
little  more  than  cut  a  shallow  valley  in  the  loose  glacial 
drift  (Fig.  483). 

Every  stream  that  enters  a  lake  is  bringing  to  it  sediment 
which  is  helping  to  fill  the  basin  ;  and  the  waves,  winds, 
and  rain  wash  add  to  this  sediment  supply.  The  finer  rock 
fragments  are  carried  out  into  the  lake  and  strewn  over  its 
bottom,  while  the  coarsest  fragments  are  deposited  near  the 
shore,  especially  opposite  the  stream  mouths,  building  deltas. 
(Figs.  107,  293,  297.) 

As  soon  as  part  of  a  lake  becomes  shallow  enough,  vege- 
tation commences  to  grow  in  the  quiet  water  (Figs.  303, 
306).     The  death  of   these  plants  —  including  lilies,  reeds. 


LAKES  AND  SWAMPS.  165 

CH»*e,  and  spliagnum  moss — supplies  further  material  for 
lake  filling.  Gradually  the  lake  is  replaced  by  a  swampy 
plain  (Fig.  304),  the  upper  layers  of  which  are  made  of 
vegetable  remains. 

Over  this  swampy  plain  the  streams  meander,  gradually  build- 
ing it  higher  by  flood  deposits  until  it  becomes  a  dry-land  plain. 
During  its  existence,  a  lake  acts  as  a  temporary  base  level,  below 
which  the  incoming  streams  cannot  cut.  But  when  a  lake  is 
filled,  the  outlet  stream,  being  no  longer  robbed  of  its  sediment,  is 
able  to  cut  more  rapidly ;  and,  as  the  outlet  stream  deepens  its 
valley,  opportunity  is  given  for  the  streams  on  the  lake  plain  to 
cut  valleys.  Then  the  sediment  with  which  the  lake  basin  has 
been  filled  is  slowly  removed.  In  the  glacial  belt  there  are 
many  illustrations  of  partly  or  completely  filled  lakes  and  ponds ; 
and  among  mountains  every  gradation  in  lake  destruction  is 
found,  even  to  the  point  where  all  lake  sediment  has  been  removed. 

Summary.  —  Lakes  are  normally  removed  by  combined  cutting  at 
the  outlet  and  filling  loith  sediment  ;  but  doivn-cutting  at  the  outlet  is 
usually  slight  because  the  outfioiving  streams  have  little  sediment. 
Plant  growth,  and  the  floods  of  streams  that  floiv  over  the  swampy 
2)lai7i,  accomplish  the  final  stage.  Wlien  filling  is  complete,  the  streams 
are  able  to  cut  into  these  lake  beds  and  remove  them. 

120.  Importance  of  Lakes.  —  Lakes  are  highly  important  as 
resorts  for  people  in  search  of  rest  and  recreation.  The 
beautiful  scenery,  cool  climate,  boating,  bathing,  and  fishing 
attract  thousands  of  people  each  summer  to  the  Great 
Lakes,  Lake  George,  Lake  Champlain,  and  the  lakes  of  the 
Adirondacks,  the  Catskills,  and  New  England. 

Lakes  have  a  decided  influence  on  climate.  In  summer  the 
water  warms  less  rapidly  than  the  land,  and  this  cools  the 
air  over  the  lakes.  In  winter,  on  the  other  hand,  when 
the  land  is  frozen  and  snow  covered,  deep  lakes  are  open  and 
the  temperature  is,  therefore,  above  freezing  point.  This 
open  water  acts  like  a  great  stove,  raising  the  temperature 
of  the  air,  which  winds  carry  to  the  neighboring  land. 


166  NEW  PHYSICAL   GEOGRAPHY, 

The  lake  water  warms  so  slowly  in  spring  that  its  presence 
chills  the  land  near  by  and  retards  the  buds  of  plants.  It  also 
helps  to  prevent  late  spring  frosts.  This  is  very  important  to. 
delicate  plants,  like  some  of  the  fruits  which  are  greatly  injured 
by  frosts  late  in  spring  after  the  buds  have  appeared.  The 
water,  warmed  in  summer,  also  tends  to  prevent  early  autumn 
frosts,  and  thus  the  growing  season  for  delicate  plants  is  pro- 
longed. For  these  reasons  lake  shores  are  often  the  seat  of 
important  fruit-raising  industries.  This  is  well  illustrated  on 
the  shores  of  the  G-reat  Lakes.  One  of  the  best  vineyard  regions 
of  the  United  States  is  along  the  south  shore  of  Lake  Erie; 
and  the  peninsula  of  Ontario,  between  Lakes  Erie,  Ontario,  and 
Huron,  has  so  moderate  a  climate  that  peaches  and  tobacco  are 
grown.     A  similar  influence  is  felt  all  along  the  Great  Lakes. 

Lakes  are  an  important  source  of  food  fish.  They  are  also  a 
source  of  ice,  which  may  be  stored  for  use  in  summer.  To  freeze 
shallow  lakes  does  not  require  great  cold ;  but  large,  deep  lakes 
rarely  freeze.  The  reason  for  this  fact  is  that,  until  a  tempera- 
ture of  39°  is  reached,  fresh  water  becomes  steadily  heavier  and 
sinks.  It  is,  therefore,  necessary  to  lower  the  temperature  o1 
the  entire  lake  to  39°  before  the  surface  freezes.  The  settling 
of  cold  water  in  winter  gives  to  the  bottom  of  deep  lakes  a  tempera- 
ture of  39°  throughout  the  year. 

Lakes  are  also  of  great  value  in  navigation.  In  early  days 
the  Great  Lakes  were  of  the  highest  service  as  pathways  for 
the  explorers  of  the  wilderness ;  to-day  they  are  thronged 
with  ships  going  in  all  directions.  By  this  lake  navigation 
and  commerce  the  location  of  several  great  cities  has  been 
determined  —  Duluth,  Milwaukee,  Chicago,  Detroit,  Toledo, 
Cleveland,  Buffalo,  Toronto,  and  others  (p.  313). 

The  building  of  railways  into  the  interio  of  Africa  is  now 
opening  up  the  great  African  lakes  to  navigation.  They  have 
already  been  important  factors  in  the  development  of  tropical 
Africa,  and  were  traversed  by  steamboats  even  at  the  time  when 
it  was  necessary  for  all  the  machinery  to  be  carried  to  them  on 
the  backs  of  men. 


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Fig.  303.  —  A  pond  in  which  vegetation  is  aiding  in  filling.    Lilies  are  the  far- 
thest out,  then  low  shrubs,  then  low  trees,  and  finally  the  forest. 


Fig.  304.  —  A  filled  pond  in  the  Adirondacks,  showing  the  swamp  plain  and  the 
stream  crossing  it.  It  is  still  too  swampy  for  trees  to  grow.  (Copyright, 
S.  R.  Stoddard,  1888.) 


LAKES  AND  SWAMPS.  167 

As  storage  basins  and  regulators  of  water  supply,  lakes  serve 
still  another  important  purpose.  While  the  volume  of  such 
rivers  as  the  Mississippi  varies  with  the  rainfall,  the  lake- 
fed  Niagara  and  St.  Lawrence  maintain  a  very  uniform  flow. 
It  is  because  they  store  large  quantities  of  water  for  steady 
supply  that  lakes  and  ponds  are  so  useful  for  city  water  sup- 
ply, for  factories,  and  for  irrigation.  The  fact  that  sediment 
settles  in  lakes  makes  them  of  further  value  in  supplying 
clear  drinking  water,  even  though  entered  by  very  muddy 
streams.  Indeed,  ponds  are  often  made  part  of  a  city  water 
supply  for  this  very  purpose  of  removing  sediment. 

The  drying  up  of  salt  lakes  leaves  beds  of  salt,  some  of  which 
are  found  on  the  surface  of  arid  lands,  as  in  western  United 
States ;  others  are  buried  deep  in  the  earth.  Dried-up  salt  lakes 
also  supply  other  mineral  substances,  one  of  the  most  important 
being  gypsum,  which  is  used  for  plaster  of  paris,  land  fertilizer, 
and  the  "  chalk  "  of  crayons. 

Summary.  —  Lakes  are  important  as  resorts  ;  they  have  decided 
influence  on  the  climate  of  near-hy  land  ;  they  are  a  source  of  ice  ; 
they  supply  food  fish  ;  they  are  very  useful  for  navigatioyi  ;  they  act 
as  storage  reservoirs  for  a  steady  supply  of  water,  and  as  settling 
basins  for  sediment  ;  and  dried-up  salt  lakes  furnish  beds  of  salt, 
gypsum,  and  other  mineral  substances. 

SWAMPS. 

121.  Causes  of  Swamps.  —  A  swamp  is  a  damp  place  on 
the  land,  not  ordinarily  covered  by  standing  water.  It  is 
caused  bv  some  interference  with  the  run-off  of  water,  such 
as  a  gentle  slope,  or  the  growth  of  swamp-loving  vegetation. 
One  of  the  most  common  causes  of  swamps  is  the  filling  of 
lakes,  forming  surfaces  so  level  that  swamp  plants  grow  there 
in  abundance.  During  the  stages  of  lake  filling,  swamps  are 
formed  on  deltas,  in  bays,  and,  if  the  lake  is  small,  even  along 
the  shores  (Figs.  303,  306) ;  and,  when  completely  filled,  the 
lake  is  replaced  by  a  swamp  (Fig.  304). 


168  NEW  PHYSICAL   GEOGRAPHY. 

In  cool,  damp,  temperate  climates,  the  most  important 
swamp-producing  plant  is  the  sphagnum  moss,  which  forms 
peat  bogs.  Sphagnum  often  grows  out  from  the  shores  of 
small,  shallow  ponds,  floating  on  the  surface  (Fig.  305),  and, 
by  the  decay  of  its  lower  parts,  causing  a  deposit  of  vege- 
table muck  on  the  bottom.  Eventually  the  sphagnum  may 
reach  entirely  across  a  pond,  with  growing  plants  above  and 
a  thick,  liquid  mass  of  decaying  vegetation  below.  It  is 
then  called  a  quaking  hog  (Fig.  305),  because  it  trembles,  or 
quakes,  under  the  foot.  If  one  sinks  into  the  muck  below, 
escape  is  impossible.  Very  perfect  remains  of  extinct  ani- 
mals, and  even  of  men,  have  been  found  in  the  peat  bogs  of 
Ireland,  the  decaying  vegetation  forming  preserving  acids 
which  interfere  with  decav. 


BOAMAt  &  C9.,  N.Vi 

Fig.  305.  — To  show  the  growth  of  sphagnum  moss  out  from  the  shore,  forming  a 
quaking  bog.  In  time  the  moss  from  the  sides  will  meet,  completely  inclosing 
the  pond,  and,  by  its  decay,  covering  the  entire  bottom  with  muck. 

Swampy  or  boggy  places  are  common  on  hillsides  where  springs 
appear,  encouraging  the  growth  of  sphagnum  and  other  swamp 
plants.  Sphagnum  holds  water  like  a  sponge,  and  is  thus  able  to 
grow  some  distance  from  the  spring ;  in  fact,  it  may  even  climb 
the  hillside,  making  a  climbing  bog.  In  the  damp  climate  of  Ire- 
land, climbing  bogs  sometimes  become  so  heavy  with  water  that 
they  slide  down  the  hillside,  becoming  "  bursting  bogs,"  by  whicli 
both  life  and  property  have  been  destroyed. 

The  Arctic  tundra,  in  winter  a  frozen,  snow-covered  desert,  in 
summer  becomes  a  vast  swamp,  wherever  there  is  soil.  The  rea- 
son for  this  is  that  the  melting  frost  makes  the  ground  wet,  as  it 
does  in  all  cold  climates  in  spring.  Every  rain  makes  the  tundra 
more  swampy,  partly  because  the  frost  prevents  the  water  from 
soaking  into  the  ground,  and  partly  because  it  helps  the  frost  to 
melt.  In  this  swampy  land  mosquitoes  develop  in  such  numbers 
as  to  become  a  great  pest. 


LAKES  AND  SlVAMPa.  169 

The  overflow  of  riveivs  causes  swamps  in  low  places  on 
floodplains,  especially  on  the  low  ground  just  belv.nd  the 
natural  levees.  These  swamps  are  unfit  ^o^  v  dtivation 
and  are  occupied  by  dense  forests  of  cypress,  black  gum, 
and  other  swamp-loving  trees  (Fig.  308).  Swamps  are  also 
found  along  the  lower  courses  of  rivers,  where  the  river 
water  is  backed  up  by  the  tide  and  caused  to  overflow  low 

land  (Fi^.  121).     ■ 

Level  coastal  plains  (p.  72)  often  have  so  gentle  a  sIojdp 
that  the  water  cannot  run  off;  and  the  drainage  is  further 
interfered  with  by  the  rank  growth  of  vegetation  which  the 
water  encourages.  Such  swamps  are  found  on  the  coastal 
plain  of  Texas  and  in  Florida  (Figs.  78,  79),  especially  in 
the  Everglades  region.  The  famous  Dismal  Swamp  on  the 
coastal  plain  of  Virginia  and  North  Carolina  is  another 
illustration  (Fig.  307).  By  clearing  off  the  vegetation,  and 
cutting  ditches  for  the  water  to  run  through,  parts  of 
Dismal  Swamp  have  been  drained. 

Naturally  there  are  few  swamps  in  arid  lands ;  but  some  are 
found  near  springs  and  on  the  river  floodplains.  There  are  also 
marshy  places — alkali  flats  and  salines  (p.  87) — in  which  only 
a  few  species  of  plants  can  grow.  At  times  of  flood  they  may 
become  shallow,  muddy  lakes,  called  play  as;  but,  at  otlier  seasons, 
evaporation  changes  them  to  hardened  mud,  crusted  over  with 
alkali  and  salt.  When  wet,  the  deep,  sticky  mud  often  makes 
them  quite  impassable. 

Swamps,  or  marshes,  are  also  found  on  the  seacoast  (pp.  216, 217). 

Summary.  —  Sicamps  are  caused  during  the  ^fiUing  of  lakes,  one 
form  of  such  swa7nps  bnug  the  peat  hog,  formed  by  the  growth  of 
sphagnum  moss.  Spyhagyiuni  also  makes  swampy  places  around 
springs,  and  climhi)ig  bogs  on  hillsides.  Hie  melting  of  frost  in 
su7nmer  catises  the  Arctic  tundra  to  be  swampy  wherever  there  is 
soil.  Swamps  also  occur  along  rivers  and  on  level  coastal  p>l(ii^is. 
In  arid  lands,  where  evaporation  causes  a  deposit  of  salt  or  alkali, 
there  are  swampy  tracts^  called  alkali  f^ats  and  salineb:  > 


170  NEW  PHYSICAL  GEOGRAPHY. 

122.  Effects  of  Swamps.  —  The  dampness  of  swamps  makes 
them  unhealthful;  and  malaria,  transmitted  b}^  mosquitoes 
which  breed  in  the  water,  prevails  in  many  swamp  regions. 
In  tropical  regions,  as  along  the  narrow  coastal  plain  of  the 
central  African  coast,  and  in  Central  America,  fever  is  so  com- 
mon that  white  men  suffer  even  in  crossing  the  level,  damp 
iowland.  Because  of  malaria,  parts  of  Italy  have  become 
quite  deserted ;  and  some  of  the  river  bottoms  and  rice 
swamps  of  the  South  have  been  left  to  the  negroes,  who 
suffer  little  from  the  unhealthful  climate. 

Swampy  conditions  unfit  land  for  most  purposes  except 
rice  production;  but,  when  drained,  the  rich,  black  soil  is 
very  productive.  For  this  reason,  as  well  as  for  the  sake 
of  health,  swamp  lands  are  being  drained,  where  possible. 
This  has  been  done  much  more  extensively  in  Europe  than 
in  America,  where  land  is  less  valuable.  The  most  exten- 
sive drainage  has  been  carried  on  in  the  Netherlands,  where 
the  low,  swampy  delta  of  the  Rhine,  and  even  part  of  the 
shallow  sea  bottom,  have  been  protected  by  dikes,  and  drained 
by  pumping.  About  one  half  of  the  Netherlands  is  reclaimed 
land,  a  large  part  of  it  being  below  sea  level. 

The  salines  of  arid  lands  have  valuable  stores  of  salt ;  and  the 
peat  bogs  of  cool  temperate  climates  are  important  sources  of 
fuel.  Coal  and  wood  are  so  abundant  in  America  that  this  source 
of  fuel  is  scarcely  touched ;  but  in  northern  Europe  it  is  a  very 
important  fuel,  being  cut  out  with  spades  (Fig.  309)  and  dried 
and  stored  for  winter.  Coal  beds  are  similar  swamp  deposits, 
made  ages  ago,  and  covered  and  preserved  beneath  thick  beds  of 
sediment.  The  swamp  deposits  of  Florida  would,  if  covered  with 
layers  of  sediment,  slowly  change  to  coal. 

Summary.  —  Swamps  are  unhealthful,  being  a  source  of  malaria  ; 
they  are  of  little  value,  unless  drained  ;  hut  the  salines  supply  salt, 
and  the  peat  bogs  fuel.     Coal  is  made  of  swamp  deposits,  slowly 
'  changed  to  mineral  and  preserved  beneath  beds  of  sediment. 


mnii^jtwi. 'Bgr'iyjfrr'.uiiu.iiii  .i.ii'iw  i     ii>"  ""tt' '   "''■""■"■"■"'■■■■"■'"  ■'«■"■' 


Fig.  306.  —  A  lake  in  the  Adirondacks  (Fifth  Lake,  Fulton  Chain)  in  whii-h 
vegetation  is  aiding  in  filling.  By  this  the  lake  shores  have  been  changed 
to  swamps.  * 


^Ef -. 


•>^"">-i-.;-_j-,#*sjT.  v!asa^:5-3!i-«?r- -.*r/ 


■■:y\   ! 


Bi.i     ■  ■ 


Fig.  307.  —  A  view  in  the  Dismal  Swamp.    The  cypress  knees  and  roots  are 
seeo  rising  to  a  level  above  the  reach  of  high  water. 


Fig.  308.  —  A  river  swamp  in  Mississippi. 


-?HWW-'t'*'HfW?« 


^=^ 


Fjg.  309. — Digging  peat  in  a  bog  in  Ireland. 


LAKES  AND   SWAMPS,  171 


Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline. —  116.  Origin  of  Lake  Basins.  —  Definition;  im. 
possibility  of  formation  of  large  basins  by  rivers ;  causes  for  lakes ;  most 
important  cause ;  combination  of  causes  ;  effect  of  beavers ;  of  man. 

117.  Size  and  Form  of  Lakes.  —  Variation  in  size;  in  depth;  long 
lakes;  irregular  lakes;  circular  lakes;  effect  of  deltas;  effect  of  waves. 

118.  Salt  Lakes.  —  (a)  Instances:  Caspian  Sea;  Dead  Sea;  Great 
Salt  Lake.  (&)  Cause :  source  of  salt ;  failure  to  overflow ;  increasing 
saltness.     (c)  Former  moist  periods :  shore  lines  ;  Lake  Bonneville. 

119.  Life  History  of  Lakes.  —  Exceptional  causes  for  removal;  cutting 
at  outlet ;  slight  importance ;  sources  of  sediment ;  places  of  deposit ; 
effect  of  vegetation  ;  change  to  dry  land;  removal  of  lake  beds. 

120.  Importance  of  Lakes.  —  (a)  Summer  resorts:  reason;  instances. 
(b)  Climate  :  summer  influence ;  winter ;  spring ;  autumn ;  effect  on 
vegetation;  illustrations.  (c)  Food  fish.  (d)  Freezing:  ice;  reason 
why  deep  lakes  do  not  freeze,  (e)  Navigation :  Great  Lakes ;  cities ; 
African  lakes.  (/)  "Water  supply :  effect  on  floods ;  storage  of  water ; 
settling  of  sediment,     (g)  Dried-up  salt  lakes  :  salt;  gypsum. 

121.  Causes  of  Swamps.  —  (a)  Definition,  (b)  Lake  swamps;  filled 
lakes;  lake  shore  swamps,  (c)  Peat  bogs:  sphagnum;  quaking  bogs; 
animal  remains,  (d)  Hillside  swamps  :  springs ;  climbing  bogs ;  burst- 
ing bogs,  (e)  Tundra  swamps :  in  winter ;  in  summer.  (/)  River 
swamps :  floodplains ;  In  lower  course.  (g)  Coastal  plain  swamps : 
cause;  illustrations;  drainage.  (A)  Arid  land  swamps:  scarcity; 
alkali  flats ;  salines ;  playa  lakes,     (i)  Seashore  swamps. 

122.  Effects  of  Swamps.  —  Effect  on  health ;  effect  on  cultivation ; 
drained  swamps ;  Netherlands;  supply  of  salt ;  of  peat;  origin  of.  coal. 

Questions.  — 116.  Why  is  it  not  possible  for  rivers  to  excavate  large 
basins?     State  the  causes  for  lake  basins. 

117.  How  do  lakes  vary  in  size  and  depth?  Inform?  Why?  What 
effects  have  deltas?     Waves? 

118.  What  is  the  condition  of  Caspian  Sea?  Dead  Sea?  Great  Salt 
Lake?     What  causes  salt  lakes?     Describe  Lake  Bonneville. 

119.  What  happens  at  the  outlet  of  most  lakes?  AV'ith  what  mate- 
rials are  lakes  filled?     What  is  the  last  stage  in  the  life  history  of  lakes? 

120.  Why  are  lakes  favorite  summer  resorts?  How  does  the  lake 
water  influence  climate?  What  effect  has  this  on  vegetation?  Why  do 
not  deep  lakes  freeze?  Give  illustrations  of  the  value  of  lakes  in  navi- 
gation. What  effect  have  lakes  on  water  supply?  What  important 
mineral  substances  are  supplied  from  dried-up  salt  lakes  ? 


172  NEW  PHYSICAL   GEOGRAPHY. 

121.  What  is  a  swamp?  In  what  ways  are  swamps  associated  witl: 
lakes?  What  are  peat  bogs?  Quaking  bogs?  Climbing  bogs?  Why- 
are  tundras  swampy  in  summer  ?  Where  near  rivers  do  swamps  occur  ? 
Why  are  swamps  common  on  coastal  plains?  Give  illustrations.  What 
are  alkali  flats  and  salines  ?    Playas  ? 

122.  What  effect  have  swamps  on  health?  What  effect  have  swamps 
on  agriculture?  How  may  they  be  made  valuable?  What  fuel  is  sup- 
plied from  swamps?     What  is  the  origin  of  coal? 

Suggestions.  —  (1)  Make  a  valley  in  clay  and  pour  water  into  it.  It 
is  a  stream  valley.  Place  a  dam  across  it  and  make  a  miniature  lake. 
What  is  its  shape?  Make  one  or  two  tributary  valleys  into  which  the 
water  rises.  What  is  the  shape  then  ?  Wash  sediment  into  the  lake  by 
sprinkling  the  sides  with  a  watering  pot.  Notice  the  growth  of  deltas. 
The  lake  may  even  be  filled.  (2)  In  a  deep  jar  of  water,  take  the  tem- 
perature at  the  top  and  bottom.  Pound  up  ice  and  put  it  into  the  jar, 
and  when  it  has  all  melted,  again  take  the  temperature  at  the  top  and  the 
bottom.  Why  has  the  bottom  water  this  temperature?  Continue  put- 
ting in  ice  until  the  temperature  at  the  surface  is  36°.  What  is  the  tern 
perature  at  the  bottom  then  ?  (3)  Place  a  large  dish  of  warm  water  in 
a  cold  room.  Does  the  temperature  of  the  air  change  as  a  thermometer 
is  brought  near  the  water  ?  Try  the  same  experiment  with  a  large  dish 
of  ice-cold  water  in  a  warm  room.  (4)  If  your  home  is  near  a  lake, 
study  it.  Can  you  find  out  what  caused  it?  Does  the  outlet  stream 
flow  in  a  deep  or  shallow  valley?  Are  there  any  deltas?  Where?  Any 
signs  of  filling  by  wave  action?  Are  there  any  swamps?  What  kinds 
of  plants  grow  on  the  shallow  lake  bottom  and  shore?  (5)  Are  there 
any  swamps  near  your  home  ?  What  is  their  cause?  Is  it  believed  that 
they  are  unhealthful?  Are  any  of  them  partly  or  wholly  drained? 
How  was  it  done  ?  What  effect  has  the  draining  had  ?  (6)  Make  three 
surf  aces  of  clay  :  (1)  a  steep  slope,  (2)  a  plain,  (3)  a  plain  with  vegetation 
(made  by  putting  pieces  of  grass  in  it).  Sprinkle  with  water.  Which 
remains  wet  longest?    Why?     Which  dries  first? 

Reference  Books.  —  Russell,  Lakes  of  North  America,  Ginn  &  Co., 
Boston,  1895,  $1.50;  Tarr,  Physical  Geography  of  Neio  York  6^to^e,  Chap- 
ter VI,  Macmillan  Co.,  N.Y.,  1902,  $3.50;  Gilbert,  Lake  Bonneville, 
Monograph  I,  U.  S.  Geological  Survey;  Lake  Bonneville,  2d  Annual, 
U.  S.  Geological  Survey,  p.  169;  Russell,  Present  and  Extinct  Lakes 
of  Nevada,  National  Geographical  Monographs,  American  Book  Co.,  New 
York,  1895,  $2.50;  Lake  Lahonton,  3d  Annual,  U.  S.  Geological  Survey, 
p.  195 ;  Lake  Lahonton,  Monograph  XI,  U.  S.  Geological  Survey ;  Mono 
Lake  Region,  8th  Annual,  U.  S.  Geological  Survey,  p.  267. 


CHAPTER   X. 


THE  OCEAN. 


123.  Importance  of  the  Ocean.  —  We  have  already  learned 
(p.  15)  that  the  ocean  is  in  many  ways  of  importance  to 
man.  It  supplies  vapor  for  rain,  and  moderates  the  climate 
of  the  lands,  it  is  a  source  of 
food  and  other  products  that 
man  needs  ;  and  it  is  an  impor- 
tant highway  of  communica- 
tion between  all  quarters  of 
the  globe. 

THE   OCEAN  BOTTOM. 

124.  Oceanography. — Ocean- 
ography is  the  study  of  the 
ocean,  both  the  surface  and 
the  bottom.  For  carrying  on 
this  study  there  have  been 
numerous  exploring  expedi- 
tions, the  most  important  be- 
ing that  of  the  British  ship 
Challenger^    which    spent   four 

years    in   studying    the    Atlan-     Fig.  310.  ^Deep-sea   sounding  Tppa- 
tic.  Pacific,  Indian,  and   South-  ratus.    ^,  cannon  bail  suspended 

ern  oceans.  Other  governments  *[«°^  ^^^^  ^'  ^Ij^^^  l^T  7^^"" 

I  .         £  the  apparatus  strikes  the  bottom, 

have    also    sent     out     ships    for  releasing  the  ball,  as  shown  in  the 

this  purpose,  among  them  the  right-hand  figure. 

U.  S.  Coast  Survey  steamer  Blake  and  the  U.  S.  Fish  Com- 
mission steamer  Albatross,     One  reason  for  a  special  study  of 

173 


"ZS" 


174 


NEW  PHYSICAL   GEOGRAPHY, 


the  ocean  is  to  determine  its  deptli  and  tlie  nature  of  its 
bottom  in  order  to  discover  proper  lines  for  submarine  cables. 
These  cables  are  so  important  in  commerce  and  war  that  lines 
now  cross  the  oceans  in  various  directions. 

To  determine  the  depth,  use  is  made  of  a  sounding  machine 
"which  lowers  an  iron  weiglit,  usually  a  cannon  ball,  to  the  bottom. 
This  heavy  weight  is  not  drawn  back  to  the  surface,  but  is  auto- 
matically released  when  botj^om  is  struck  (Fig.  310). 

A  sample  of  the  ocean-bottom  water  is  brought  up  in  a  metal  tube, 
or  water  bottle  (  T,  Fig.  310),  which  remains  open  on  the  way  down, 
but  closes  when  drawn  up.  A  sample  of  the  ocean-bottom  mud 
clings  to  soap  or  tallow  placed  on  the  bottom  of  the  water  bottle ; 
and  the  temperature  is  determined  by  thermometers  attached  at 

various  points  on  the 
sounding  line.  These 
deep-sea  thermome- 
ters are  so  made  that 
they  record  the  tem- 
perature at  the  point 
from  which  they  are 
drawn  up.  Thus, 
by  a  single  sound- 
ing, the  depth,  some 
of  the  water,  a  sam- 
ple of  the  bottom, 
and  the  temperature 


eoRMAv  *  CO..  N.Y.     of  the  water  at  vari- 
FiG.  311.  — Apparatus   used    by  the     Challenger    in     OUS     points     are    all 
(?  is  a  weight,  and  B,  C,  B,  E,  and  F    obtained. 


dredjrins:. 


represent  various  jjositions  of  the  dredge.  ,r  , 

Most  deep-sea  ex- 
ploring expeditions  also  make  a  study  of  the  animal  life  of  the 
ocean  bottom.  Specimens  of  these  animals  are  obtained  by  means 
of  a  deep-sea  dredge,  or  trawl  (Fig.  312),  which  consists  of  an  iron 
frame  several  feet  in  length  with  a  long  bag  net  attached.  This 
is  dragged  over  the  ocean  bottom  (Fig.  311),  animals  in  its  path 
being  scooped  up  by  the  frame  and  gathered  in  the  bag.  Many 
v(rf^}vd  creatures  arft  thus  obtained. 


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Fig.  314.  —  The  depths  of  the  Atlantic  in  fathoms  (a  fathom  is  six  feet).  The 
mid-Atlantic  ridge  is  called  Dolphin,  Connecting,  and  Challenger  plateaus. 
Note  the  continental  shelves,  dotted. 


^  el  ^-^^^ 


^       SHtUF     ;    !    ;       ,    ^^     I 53^ I LEVEL  r^o,        t  'i^J^ 


FiQ.  315.  —  Section  to  show,  in  diagram,  the  conditions  of  temperature  and  depth 
in  the  Atlantic.  Ocean  depth  and  width  of  continental  shelf  greatly  exagger- 
ated.   The  raised  portion  in  the  center  represents  the  mid-Atlantic  ridgfr 


THE  OCEAN, 


175 


5i»ammary.  —  For  a  study  of  the  ocean,  or  oceanography,  there 
have  been  numerous  government  exploring  expeditions,  one  of  whose 
objects  has  been  to  determine  the  best  lines  for  cables.  In  the  study 
of  the  ocean  bottom  the  depth,  nature  of  the  water,  nature  of  the  bot- 
tom, temperature,  and  kind  of  animal  life  are  usually  determined. 

125.  Ocean  Basins.  —  Exploration  has  shown  that  the 
ocean  bottoms  are  mainly  vast  submarine  plains  (Figs.  313, 
316).  Beyond  the  continental  slopes  (p.  22)  almost  the  entire 
ocean     floor     is     a 

Tnonr»fr»-nrMiG     nlnin  Eastern  Overflowed 

lUUnOLOIlOUb     pi  dill,         United  States  margin  of  the 

1  j_  y^y^^'-^K^^  Continent  Sea  Level 

occupying  about  ^ — -^=""~— ^ "  r-^tmmo^m^^^j:^ 
earth's  surface  (Fig.     ^^^^^^^^^^^^^^S^: 

19).  Here  and  Fig.  316.  —  Rising  of  the  ocean  water  over  the  con- 
there    a     portion     is  tinental  slope  overflowing  the  continent  margin 

^  or  shelf  (p.  72). 

sunk  below  the  rest, 

forming  a  deep  (Fig.  314)  ;  and  here  and  there  volcanic 
peaks  or  mountain  ridges  rise  from  the  ocean  floor  (Fig.  313), 
sometimes  reaching  above  the  surface.  But  these  elevations 
and  depressions  are  only  exceptions  to  the  general  levelness. 

The  Blake  deep,  not  far  from  Porto  Rico,  is  the  deepest  known 
point  in  the  Atlantic  Ocean,  27,360  feet  (Fig.  313).  There  are  a 
number  of  volcanic  peaks  in  the  Atlantic,  such  as  the  Bermudas, 
the  Azores,  the  Canaries,  Cape  Verde  Islands,  and  St.  Helena. 
In  the  mid-Atlantic  there  is  a  low,  irregular  elevation,  or  a  series 
of  submarine  plateaus  (Fig.  314),  sometimes  called  the  mid-Atlantic 
ridge  (Fig.  315).  There  are  deeps  on  both  sides  of  it.  This 
upraised  portion  extends  the  whole  length  of  the  Atlantic,  usually 
several  thousand  feet  beneath  the  surface. 

There  are  hundreds  of  volcanic  peaks  in  the  open  Indian  and 
Pacific  oceans  (Fig.  313),  usually  in  chains  along  the  crests  of 
submarine  mountain  uplifts,  —  for  example,  the  Hawaiian  chain, 
and  the  Ladrone  chain,  of  which  Guam  is  one  peak.  The  deepest 
known  point  in  any  ocean,  31,600  feet,  is  the  Challenger  deep,  near 
Guam.  The  Aldrich  deep,  near  New  Zealand,  is  30,930  feet; 
and  the  Tuscarora  deep,  east  of  Japan,  27^930  feet. 


176 


NEW  PHYSICAL   GEOGRAPHY. 


Little  is  known  about  the  Arctic  and  Southern  oceans;  but 
Nansen  found  a  depth  of  over  12,000  feet  in  the  Arctic,  and  parts 
of  the  Southern  Ocean  are  also  known  to  be  very  deep. 

Summary.  —  Beyond  the  continental  slope  is  a  vast  expanse  of 
plain,  covering  about  tico  thirds  of  the  earth's  surface.  There  are 
occasional  deeps  sunk  beloio  its  general  level,  and  volcanic  cones  and 
mountain  ridges  rising  above  it. 

126.  Deposits  on  the  Ocean  Bottom.  —  (A)  Rock  Frayments. 
—  The  wind,  rain,  rivers,  and  waves  drag  fragments  from  the 
land  into  the  sea.  Most  of  this  sediment  settles  in  the  quiet 
water  near  the  coast ;  but  currents  drift  some  of  the  liner 
particles  out  to  sea,  even  to  the  edge  of  the  continental  shelf. 
This  sediment  fills  depressions  and  tends  to  smooth  over 
the  irregularities  of  the  continental  shelf ;  and,  by  its  accu- 
mulation, it  makes  beds  of  sedimentary  rock,  coarsest  near 
the  coast  (p.  32).  Remains  of  ocean  animals  also  accumu- 
late on  the  bottom  and  add  to  the  deposit  of,  sediment,  being 

preserved    in    the 
rocks  as  fossils. 

Summary. — Near 
the  continents  the 
ocean  bottom  is  cov- 
ered ivith  layers  of 
rock  fragments  de- 
rived from  the  land 

(B)  Oeean-hoi- 
toin  Oozes.  —  So  lit 
tie  rock  waste  io 
(lra«"or-ed  far  out  to 
sea  that  the  contri- 
bution of  animal 
remains  exceeds  that  of  rock  waste.  More  than  a  third  of 
the  ocean  bottom  is  covered  with  an  ooze,  composed  mainly 
of  animal  and  plant  remains.     This  deposit  contains  a  small 


Fig.  317. 


A  magnified  sample  of  globigerina  ooze 
I'rom  the  ocean  bottom. 


THE  OCEAN, 


111 


percentage  of  rock  fragments,  especially  pieces  of  volcanic 
ash  and  pumice  that,  on  becoming  water-logged,  have  settled 
to  the  bottom.  The  ocean-bottom  ooze  is  made  partly  of 
organisms  that  live  on  the  bottom,  but  mainly  of  the  shells 
of  microscopic  organisms  that  live  in  vast  numbers  in  the 
surface  waters  and,  on 
dying,  settle  to  the 
bottom. 


The  ocean-bottom  ooze 
is  given  different  names 
according  to  the  organ- 
isms that  are  most  abun- 
dant Thus  a  large  part 
of  the  ocean-bottom  de- 
posit is  called  glohigerina 
ooze  (Fig.  317),  because  of 
the  abundance  of  micro- 
scopic Globigerina  (Fig. 
318).  Chalk  is  a  similar 
ooze  deposited  on  the 
bottom  of  ancient  seas. 
There  is  alsopteropocZ  and 
diatom  ooze.  The  latter 
is  made  of  siliceous  parts 
of  microscopic  diatom 
plants  which  thrive  espe- 
cially in  the  cold  waters 
of  the  Southern  Ocean. 


Fig.  318. 


-  A  specimen  of  Globigerina  from  the 
surface,  greatly  magnified. 


Summary.  —  Far  from  land,  tvJiere  there  is  Utile  rock  waste,  the 
ocean  bottom  is  covered  with  glohigerina  ana  other  oozes,  made  largely 
of  the  remains  of  organisms,  mostly  microscoinc  surface  forms. 

(C)  Bed  Olay.  —  The  shells  that  sink  to  make  globigerina 
ooze  are  composed  of  carbonate  of  lime,  but  contain  a  very 
small  percentage  of  other  substances,  such  as  iron  and  silica. 
In  the  very  deep  ocean  water  (12,000  to  15,000  feet  or  more)> 


178  NEW  PHYSICAL   GEOGHAPHT. 

which  contains  much  carbon  dioxide,  these  limy  shells  are 
dissolved  ;  but  the  iron,  silica,  etc.,  are  not  so  readily  soluble, 
and  they  pass  on  to  the  bottom  forming  a  clay,  colored  red 
by  iron  oxide.  More  than  a  third  of  the  ocean  bottom  is 
covered  with  this  red  clay,  whose  rate  of  deposit  must  be  very 
slow  since  it  is  formed  of  the  very  small  insoluble  portion  of 
shells  that  are  themselves  microscopic. 

Other  facts  further  prove  that  the  red  clay  is  formed  with 
wonderful  slowness.  Scattered  through  it  are  fragments  of 
pumice,  bits  of  meteoric  iron,  the  teeth  of  sharks,  and  the  ear 
bones  of  whales.  There  are  not  many  whales  or  sharks  in  one 
place,  nor  are  many  meteorites  falling.  If  the  red  clay  were  not 
accumulating  very  slowly,  these  objects  would  be  so  deeply  covered 
that  a  small  dredge  would  rarely  find  any  5  yet  deep-sea  dredging 
often  brings  them  to  the  surface. 

Summary.  —  Bed  day  covers  the  deeper  j^cirts  of  the  ocean  bottom  ; 
that  is,  over  one  third  of  the  entire  ocean  floor.  It  is  a  very  sloicly 
forming  deposit,  made  of  the  insoluble  remnants  of  microscopic  shells 
that  have  been  dissolved  in  the  deep-sea  water. 

127.  Land  and  Ocean-bottom  Topography.  —  There  are  three 
important  reasons  why  the  ocean  bottom  is  far  more  regular 
than  the  land  surface  (p.  21).  (1)  While  mpuntain  folding 
and  volcanic  action  cause  irregularities  both  on  land  and  ocean 
bottom,  they  are  less  important  in  the  sea  than  on  the  land. 

(2)  Erosion  sculptures  the  land  into  hills  and  valleys ;  but 
the    ocean    water   protects   tlie    bottom   from   these  agents. 

(3)  Sediment  washed  from  the  lands,  and  the  settling  of 
organisms  to  the  bottom,  tend  to  smooth  the  sea  floor. 

Because  of  these  facts,  if  a  smooth  sea-bottom  plain  is 
raised  into  the  air,  it  is  soon  carved  by  erosion  into  a  series 
of  hills  and  valleys;  but  if  a  1  irregular,  hilly  land  is  sunk 
beneath  the  sea,  it  is  soon  smoothed  over  by  a  blanket  of 
sediment  (p.  72).  There  is  a  striking  difference  between 
the  widespread  smoothness  of  ocean-bottom  plains  and  the 
pleasing  irregularity  of  the  lands. 


THE  OCEAN.  179 

Summary.  —  The  ocean  bottom  is  far  smoother  than  the  lands 
because  of  (1)  less  mountain  folding  and  volcanic  action  ;  (2)  ab- 
sence of  erosion  ;  and  (3)  widespread  deposit  of  sediment, 

THE   OCEAN    WATER. 

128.  Surface  of  the  Sea. — Elevations  on  the  land  are 
measured  from  sea  level,  by  which  is  meant  the  approach 
to  a  spherical  form  which  the  water  assumes  under  the  pull 
of  gravity  (p.  8).  The  level  of  the  sea  is  not  perfectly  in 
accord  with  the  spherical  form  of  the  earth  ;  for  the  curved 
water  surface  is  distorted  a  little  by  the  attraction  of  the  con- 
tinents, slightly  raising  its  level  near  the  coast.  Winds  and 
storms  (p.  271)  cause  local  disturbances  of  sea  level  ;  but,  as 
soon  as  the  disturbing  cause  has  passed,  gravity  draws  the 
water  back  to  its  former  level. 

There  are  two  causes  which  are  slowly  operating  to  change 
the  level  of  the  sea.  The  less  important  of  these  is  the  deposit 
of  sediment,  which  tends  to  slowly  raise  sea  level.  It  would 
take  long  periods  of  time  for  this  to  produce  a  great  effect,  fc*r 
there  is  a  vast  amount  of  water  to  be  raised.  Even  if  all  of  North 
America  above  sea  level  were  put  into  the  Atlantic,  the  surface  of 
the  oceans  would  not  be  raised  many  feet.  The  second  cause  for 
change  in  level  is  movement  of  the  ocean  bottoms.  There  is  good 
reason  for  believing  that,  during  past  ages,  the  ocean  basins  have 
been  slowl}^  growing  deeper.  The  effect  of  such  a  movement 
would  be  to  gradually  withdraw  the  waters  from  the  lands. 

Summary.  —  Sea  level  is  slightly  disturbed  by  the  attraction  of  the 
continents  ;  locally,  and  for  short  times,  by  loinds  and  storms  ;  and 
very  sloivly  by  (1)  the  deposit  of  sediment  in  the  oceans  and  (2)  the 
sinking  of  the  ocean  bottom. 

129.  Composition  of  Sea  Water. — Every  one  is  familiar  with 
the  saltness  of  the  sea.  Probably  salt  and  other  mineral  sub- 
stances were  held  in  solution  when  the  oceans  first  gathered  ; 
but  certainly  some  is  being  added  every  day.     The  vapor 


180  NEW  PHYSICAL   GEOGRAPHY. 

that  rises  from  the  ocean  does  not  remove  these  mineral 
substances  ;  but  when  it  falls  on  the  land  as  rain,  it  begins 
to  wash  more  dissolved  mineral  matter  into  the  sea  (p.  51). 
It  would  seem,  therefore,  that  the  ocean  must  be  growmg 
steadily  Salter. 

About  three  and  a  half  per  cent  of  ocean  water  is  dissolved 
mineral  matter,  more  than  three  quarters  of  which  is  common 
salt.  Magnesium  chloride  and  magnesium,  calcium,  and 
potassium  sulphates  are  also  present ;  and,  in  very  small 
q-uantities,  there  are  many  other  substances,  even  including 
compounds  of  gold  and  silver.  If  all  the  salt  of  the  oceans 
could  be  removed,  it  would  make  a  layer  about  400  feet  thick 
over  the  earth.  In  many  places  where  the  climate  is  dry,  salt 
is  obtained  by  evaporating  sea  water;  and  many  salt  beds, 
like  that  in  central  New  York,  were  formed  in  past  ages  by 
the  evaporation  of  the  water  in  arms  of  the  sea,  cut  off  as  the 
Caspian  is  to-day. 

Carbonate  of  lime,  though  present  in  very  small  quanti- 
ties, is  another  important  mineral  substance  in  sea  water. 
Many  ocean  animals,  such  as  corals  and  shell-fish,  use  it  in 
the  growth  of  their  shells  and  skeletons.  On  the  death  of 
the  animals  these  have  accumulated  in  beds  of  limestone 
which,  raised  to  form  land,  are  now  used  in  building,  smelt- 
ing iron,  and  making  lime. 

Some  air  is  mixed  with  all  ocean  water,  being  present  even 
on  the  ocean  bottom,  where  it  is  brought  by  slowly  moving 
currents.  A  few  sea  animals,  sucli  as  the  seals  and  whales, 
come  to  the  surface  to  breathe  ;  but  the  great  majority  vo,- 
(]uire  so  little  oxygen  that  they  are  able  to  obtain  what  tiiey 
need  from  the  air  that  is  mixed  with  the  sea  water.  With- 
out it  most  of  the  ocean  animals  could  not  live. 

Summary.  —  Salt  and  other  mineral  substances,  incladiug  carbon- 
ate of  lime,  of  which  shells  are  made,  are  hei)i(/  constantly  -washed 
from  the  land  into  the  sea.  Air  mixed  with  the  wat^r  supplies  the 
oxygen  which  makes  most  of  the  ocean  life  possible. 


THE  OCEAN,  181 

130.  Density  and  Pressure  of  Sea  Water.  —  Salt  water  is 
heavier,  or  has  a  greater  density,  than  fresh  water.  Calling 
fresh  water  1,  the  average  density  of  ocean  water  at  the 
surface  is  about  1.026.  The  den^'ity  is  less  than  the  average 
in  the  rainy  tropical  belt,  and  paso  near  the  mouths  of  great 
rivers,  where  a  large  amount  of  fresh  Vv^ater  is  added.  It  is 
greater  than  the  average  where  there  is  much  evaporation,  as 
in  the  dry  trade-wind  belt,  and  in  seas  inclosed  by  warm, 
arid  lands,  like  the  Red  and  Mediterranean  seas. 

There  is  an  enormous  pressure  on  the  bottom  of  deep 
oceans.  At  the  depth  u;  y,  mile  every  square  inch  bears  a 
weight  of  over  a  ten  of  water,  and  tlie  pressure  on  the 
bottom  of  the  Aldrich  deep  is  nearly  six  tons  to  every  square 
inch.  One  might  expect  that  so  great  a  weight  of  water 
would  crush  t.^Q  animals  on  the  ocean  bottom  ;  but  it  pro- 
duces no  more  effect  on  them  than  does  the  weight  of  air 
(about  15  pounds  to  the  square  inch)  which  our  bodies  bear. 

The  reason  why  this  great  pressure  is  not  felt  is  that  it  affects 
all  parts  of  the  body,  both  within  and  without.  When  deep-sea 
fishes  are  brought  to  the  surface,  however,  .and  the  pressure 
from  outside  is  reduced,  that  from  within  opens  cracks  in  their 
bodies  and  often  causes  their  eyes  to  protrude. 

Water,  unlike  air,  is  not  much  compressed,  even  under  the  great 
load  that  wei.^hs  down  on  the  bottom  lavers.  Therefore  its 
density  at  the  bottom  does  not  differ  greatly  from  that  at  the 
surface.  If  it  were  much  compressed,  as  air  is,  it  might  become 
so  dense  that  objects  could  not  sink  through  it  to  the  bottom. 
They  would  then  float  around  in  the  dense  layers. 

Summary.  —  Salt  water  is  denser  than  fresh  water ;  hut  its  density 
varies  somewhat.  There  is  an  enormous  pressure  on  the  ocean  bot- 
tom,' hut,  since  water  is  not  much  compressed  under  pressure,  its 
density  is  not  greatly  increased  at  the  hottom. 

131  Color  and  Light.  —  Sunlight  illuminates  the  upper  layers 
of  the  sea  and  reaches  to  the  bottom  of  shallow  water.  The 
beautiful  blue  of  the  open  ocean  is  partly  due  to  the  reflection  of 


182 


NEW  PHYSICAL   GEOGRAPHY, 


the  color  of  the  sky,  but  chiefly  to  the  same  cause  which  makes 
the  sky  blue  (p.  233).  Sunlight  is  made  of  waves  of  many  colors, 
and  in  their  passage  through  the  water  they  are  separated,  or 
scattered,  some  of  them  (the  indigo  and  blue)  being  reflected  back, 

giving  the  water  its  color.  Near  the  shore, 
where  there  is  more  sediment,  the  green  waves 
are  reflected,  giving  the  water  its  green  color. 
The  yellow  water  near  the  mouth  of  the  Yel- 
low Eiver  of  China  is  colored  by  the  mud 
that  the  river  brings ;  the  color  of  the  E-ed  Sea 
is  due  to  minute  reddish  organisms  that  float 
in  it. 

'No  sunlight  penetrates  to  the  bottom  of  the 
deep  sea,  which  is  darker  than  the  darkest 
night.  Having  little  use  for  eyes,  many  of  the 
deep-sea  fish  are  blind ;  but  others  have  eyes, 
and  many  are  brilliantly  colored.  These  eyes 
and  colors  are  doubtless  of  use  because  of  the 
phosphorescent  glow,  like  that  of  the  firefly, 
which  many  deep-sea  animals  emit.  Indeed, 
some  of  the  fish  have  feelers,  phosphorescent 
on  the  end,  which  have  been  called  deep-sea 
lanterns.  Phosphorescence  is  also  emitted  by 
many  surface  animals,  and  a  boat  often  leaves 
behind  it  a  trail  of  faint  phosphorescent  light, 
made  by  the  multitude  of  animalculse  that  its  passage  has 
disturbed. 

Summary.  —  The  color  of  the  sea  is  due  to  the  scattering  of  the 
waves  that  compose  white  light,  and  the  refection  of  some  of  them, 
such  as  green,  blue,  or  indigo.  No  sunlight  reaches  the  ocean 
bottom,  hut  some  of  the  animals  emit  a  phosj^horescent  glow. 

132.  Temperature  of  the  Oceans.  —  The  surface  layers  of 
ocean  water  are  warmed  by  the  sun.  Accordingly,  while  the 
waters  of  the  frigid  zones  are  nearly  at  the  freezing  point 
of  salt  water  (28^  or  29°),  tropical  waters  are  warmed  to 
80**  or  Sd"  (Fig.  320).     In  the  inclosed  Red  Sea,  where  the 


Fig.  319.  — Normal 
descent  of  ocean 
temperature  at 
the  equator. 


LINES   SHOWING 

The  Jh'aii  Itiifiial  ~^~' 

Surface  Temperature 

(iv    THE    0(FiN.       80° 


_rV       ANTARCTIC   CIRCLE 


],. 


i,- 


HO 


Fig.  320.  —  Ocean-surface  temperature.  The  effect  of  the  land,  and  of  ocean 
currents,  makes  the  temperature  lines  of  the  northern  ocean  far  more  irregu- 
lar than  those  in  the  southern  hemisphere.  On  an  outline  map  of  the  world 
make  a  sketch  map  similar  to  this. 


Fig.  321.  — The  advance  of  waves  on  a  beach,  forming  surf. 


Fig.  322.  —  A  United  States  government  ship  (the  Wateree)  stranded  on  the 
land  in  Chile  by  an  earthquake  wave  in  1869.  The  surf  line  is  seen  one 
eighth  of  a  mile  beyond  the  farther  ship. 


Fig.  323. — The  bore  wave  at  Moncton.  New  Brunswick. 


THE  OCEAN. 


183 


entrance  of  cooler  currents 
is  impossible,  the  temper- 
ature may  rise  to  90° 
or  95°.  Ocean  currents 
greatly  influence  the  tem- 
perature of  ocean  water 
(p.  194). 

Since  the  sun's  rays 
penetrate  only  the  upper 
layers  of  the  ocean,  deep- 
t?ea  water  is  not  directly 
influenced    by    them.       If 

the  surface  water  is  warm,     Fig.  324.—  Section  of  the  ocean  from  New 

the  temperature    decreases  York  to   Bermuda,  showing  the  tem- 

.--.,,  ,  perature  at  various  depths. 

rapidly  in  the  upper  layers, 

then  slowly  down  to  the  bottom  (Figs.  319,  324).     Every- 
where, even   in   the    torrid   zone,   the    temperature    of    the 

ocean  bottom  is 
low  (Fig.  325); 
and  about  four 
fifths  of  the  ocean 
water  has  a  tem- 
perature of  less 
than  40°. 


The  explanation 
of  the  cold  water 
in  the  deep  sea  is 
that  water  becomes 
more  dense  on  cool- 
ing, and  conse- 
quently sinks. 
While  fresh  water 
ceases  sinking  at 
39°  (p.  166),  salt 
water   continues   to 


35-36 


EXPLANATION 
3C-37  iiH      37-38  i 


38-39MH     +a9J^n 


BORMAr   i   CO..    N.Y. 


Fig.  325.  —  Temperature  on  the  bottom  of  the  North 
Atlantic.  The  band  of  higher  temperature  is  on 
the  mid- Atlantic  ridge  (see  Fig  3?^,. 


184 


NEW  PHYSICAL  GEOGRAPHY. 


Ocean  ^urfaee 


.§1 


30.5" 


i.OOO  Fathoms 


QULF  OF  MisXICO 
39.5 


ATLANTIC  OCEAN 


2.000   Fathoms 


.35" 


e:fiMAY    &    CO        N.V. 


increase  in  Jensity,  and,  therefore,  to  sink,  almost  until  its  freez- 
ing point  is  reached.  For  this  reason  ocean-bottom  water  is  much 
colder  than  that  on  the  bottom  of  lakes  ;  it  may,  in  fact,  be  as  low 
as  29°,     The  settling  of  cold  water  in  the  frigid  and  cold  temperate 

zones  starts  a  slow 
circulation  along  the 
ocean  bottom  toward 
the  warm  belt,  where 
there  is  a  slow 
rising.  It  is  this 
circulation  which 
supplies  deep-sea 
animals  with  the 
air  they  need  for 
breathing. 

One  of  the  best  proofs  of  this  slow  circulation  is  furnished  by 
such  seas  as  the  Gulf  of  Mexico  and  the  Mediterranean,  which 
are  partly  shut  off  from  the  open  ocean.  In  these  seas  the  de- 
crease in  temperature  continues  down  to  the  level  of  the  barrier, 
but  no  lower,  because  the  coldest  water  that  can  creep  into  them 
is  that  at  the  level  of  the  barrier  (Fig.  326). 

Summary.  —  The  temperature  of  the  surface  water  varies  with  the 
climate  ;  hut  settling  of  cold  water,  causing  a  slovj  circulation,  makes 
the  deep  sea  everywhere  cold.  Inclosed  sea  bottoms  have  the  same 
tem^perature  as  that  of  the  op)en  ocean  at  the  level  of  the  harrier. 


y  iG.  326.  —  The  temperature  in  the  Atlantic  at  a  depth 
of  2000  fathoms  is  35° ;  but  in  the  Gulf  of  Mexico, 
at  that  depth,  only  39.5°,  which  is  the  temperature 
at  the  depth  of  the  barrier  (1000  fathoms)  over 
which  the  water  enters  the  Gulf  from  the  Atlantic. 


MOVEMii^NTS   OF   THE   OCEAN   WATER. 

133.  Wind  Waves.  —  Blowing  on  the  surface  of  a  dish  of 
water  causes  small  waves.  These  are  similar  to  the  large 
waves  raised  on  the  ocean  by  the  friction  of  winds  that  blow 
over  its  surface.  The  water  itself  does  not  advance  with  the 
wave,  but  moves  up  and  down,  with  a  slight  forward  and 
backward  movement.  It  is  the  form  of  the  wave  that  ad- 
vances, as  a  wave  may  be  made  to  pass  through  a  rope  by 
shaking  it  vigorously.     Therefore  a  boat,  instead  of  moving 


THE  OCEAN.  185 

forward,  rises  and  falls  as  each  wave  passes  under  it;  but  it 
is  also  carried  forward  and  backward  a  little. 

Some  of  the  great  ocean  waves,  raised  during  heavy  gales, 
have  a  height  of  from  30  to  50  feet,  measured  from  the  top,  or 
crest,  to  the  depression,  or  trough,  between  two  waves.  Then 
the  sta  presents  a  wild  sight,  as  the  great  waves  come  down  upon 
a  ship,  their  crests  broken  and  whitened  by  the  fierce  wind. 
The  wind  mixes  much  air  with  the  ocean  water  in  the  foam  and 
spray  of  these  white  crests,  or  ivJiitecaps  (Fig.  341). 

Such  waves,  moving  at  the  rate  of  40  or  50  miles  an  hour,  some- 
times dash  over  the  decks,  carrying  all  loose  objects  along,  and 
even  tearing  away  massive  wood  and  iron  work.  Even  great 
ocean  steamers  are,  at  times,  forced  to  change  their  course  to  avoid 
the  danger  of  being  upset  by  the  approach  of  these  huge  waves 
from  one  side.  To  smaller  boats  they  are  very  dangerous,  and 
many  a  fishing  schooner  (Fig.  341)  has  been  sunk  by  them. 

The  use  of  oil  at  sea  is  now  common  in  violent  gales.  Dropped 
on  the  surface,  the  oil  spreads  in  all  directions ;  and,  as  the  oily 
surface  offers  less  resistance  to  wind,  the  waves  are  much  less 
broken.     There  is  then  less  danger  of  waves  coming  aboard. 

Waves  often  appear  when  no  wind  is  blowing,  and  even  when  the 
sea  is  smooth  and  glassy.  They  were  formed  in  some  place  where 
the  wind  was  high,  and  have  traveled  far  beyond  their  place  of 
origin.  Such  waves  are  known  as  rollers,  or  ground  swell.  Because 
waves  travel  so  far,  no  part  of  the  open  ocean  is  ever  entirely 
free  from  some  form  of  wave  or  swell. 

In  shallow  water  the  free  movement  of  waves  is  interfered 
with  by  the  bottom,  the  wave  grows  higher,  its  front  becomes 
steeper,  and  it  finally  topples  over  (Fig.  327).  Tlien  tons  of 
water  are  hurled  bodily  forward  as  surf  or  breakers  (Fig.  321), 
striking  the  shore  with  tremendous  force. 

A  current,  called  the  undertow  (Fig.  327),  flows  outward  along 
the  bottom  beneath  the  incoming  breakers.  On  many  wave- 
beaten  coasts  the  undertow  is  so  strong  as  to  be  a  source  of 
danger  to  bathers,  who  are  caught  by  it  and  held  under  water. 


186  NEW  PHTiSlCAL   GEOGRAPHY, 

Some  of  the  rock  fragments  that  are  dislodged  from  cliffs  and 
ground  up  on  the  beaches,  are  moved  offshore  in  the  undertow. 
Others  are  pushed  along  the  coast  (1)  by  the  breaking  of  waves 
which  reach  the  coast  diagonally,  and  (2)  by  the  slow  wind- 
formed  surface  current  (Fig.  327),  which  moves  in  the  direction 
the  wind  is  blowing. 


Fig.    327.  — Diagram  to  show  approach  of  a  wave  upon  a  beach. 

Summary. —  Waves,  caused  by  friction  of  ivind,  are  a  rising  and 
falling  of  the  wafer,  the  icave  form  moving  forward,  often  far  beyond 
the  place  of  origin.  They  break  on  the  coast  with  great  for  e,  tearing 
rocks  from  the  cliffs  and  grinding  them  on  the  beachei,.  moving 
some  of  the  fragments  offshore  in  the  undertow,  some  along  the  coast 

134.  Other  Waves.  —  Tap  lightly  on  the  bottom  of  a  pan 
of  water,  and  the  water  rises  in  a  low  dome.  An  earthquake 
shock  in  the  ocean  produces  a  similar  wave,  reaching  from 
the  bottom  of  the  sea  to  the  surface.  The  water  may  not  be 
raised  more  than  a  fraction  of  an  inch,  but  the  disturbance 
is  so  deep  and  affects  so  much  water  that,  \vhen  the  wave 
approaches  a  neighboring  coast,  it  rises  higher  and  higher. 
Such  a  wave  may  then  rise  to  a  height  of  more  than  100  feet, 
rushing  perhaps  a  mile  or  more  inland,  carrying  everything 
before  it,  and  leaving  vessels  stranded  (Fig.  322).  Tens  of 
thousands  of  people  have  been  drowned  by  a  single  earth- 
quake wave  (p.  119). 

Fortunately  such  waves  are  not  common  in  many  parts  of  the 
world,  though  Japan,  the  East  Indies,  and  the  coast  of  Chile  and 
Peru  are  subject  to  them.  The  waves  travel  great  distances, 
some  from  Asia  reaching  the  California  coast;  but,  so  far  a^^ay, 
they  are  too  much  spread  out  to  be  destructive. 

The  discharge  of  an  iceberg  from  a  glacier  (p.  l-4o),  or  the 
breaking  up  uf  an  iceberg  as  it  runs  aground,  starts  a  similar 


Fig.  328.  —  High  tide  near  Bourne,  Mass. 


r 


r' 

■-^^ 

■»«U^.««M, 

B-                                                                                                                -  „  - 

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^— - 

■•ymmm^  '^. 

m 

e-  ^                            -.      ' 

IttMB^-'-— 

'""T^^^. 

IS^ 

.-.■  -'  ."--■'^""■■'.  - 

Wti^^St: 

iiM^' 

-,       - 

':-,'^i;<; 

■'"'.,'(■  "ft'Wi  ,.•-♦.            •■,^"/      fiS 

i 

iddi' :■:<■[. 

■■:\)--  - 

Fig.  3S9.  —  Low  tide  at  same  place  as  above.    Describe  the  diffex'ence 


Fig.  330.  —  Low  tide  at  Gloucester  harbor,  Mass.,  where  the  tide  rises  8  or  10 
feet.    At  high  tide  a  fishing  schooner  (Fig.  34l)  can  come  in  beside  the  wharf. 


Fig.  331. Low  tide  along  the  coast  north  of  Boston,  showing  the  seaweed  mat 

which  covers  the  rocky  coast,  protecting  it  from  wave  attack.    At  high 
tide  the  wat6r  reaches  above  the  dark-colored  zone  of  seaweed. 


THE  OCEAN,  187 

wave.     These  iceberg  waves  dash  on  the  shores  with  great  force, 
reaching  several  feet  above  the  normal  level  of  the  waves. 

A  wave  of  high  water  accompanies  hurricanes  and  other  violent 
storms  at  sea  (p.  271). 

Summary.  —  Waves  are  also  started  by  earthquake  shocks  on  the 
ocean  bottom;  by  the  breaking  off  or  stranding  of  icebergs;  and  by 
violent  storms  at  sea. 

135.  Tides.  —  Twice  each  day  (more  exactly,  every  12 
hours,  26  minutes)  the  passage  of  tidal  waves,  formed  by  the 
attraction  of  moon  and  sun  (Appendix  E),  causes  the  ocean 
surface  to  rise  and  fall  (Figs.  328,  329).  In  the  open  ocean 
the  difference  in  height  between  high  and  low  tide,  or  the 
tidal  range^  is  not  over  one  or  two  feet ;  but,  as  the  tidal 
wave  approaches  the  coast,  its  height  is  increased  (Figs.  330, 
331)  by  the  effect  of  the  shallowing  bottom. 

In  the  ocean,  and  on  open  coasts,  the  tide  is  merely  a  rise 
and  fall  in  the  water  level ;  but  in  bays  and  estuaries  this 
change  in  level  starts  currents,  which  often  move  with  great 
velocity.  Such  currents  may  m(?"e  so  rapidly  that  boats 
cannot  make  headway  against  thci,^ ;  indeed,  in  the  Bay  of 
Fundy  the  tide  advances  over  the  mud  flats  more  rapidly 
than  a  man  can  run.  From  this  it  is  evident  why,  as  the  tide 
rises  and  falls,  it  is  said  to  "  come  in  "  and  *'  go  out."  The 
rising  tide  is  called  ih.^  Jlow^  the  falling  tide  the  ehh. 

The  advancing  tidal  wave  is  greatly  influenced  by  the  form  of 
the  coast.  Ordinarily  the  tidal  range  is  between  3  and  10  feet ; 
but  in  narrowing,  V-shaped  bays  the  range  is  greatly  increased,  as 
in  the  Bay  of  Fundy  in  Nova  Scotia  and  Ungava  Bay  in  northern 
Labrador,  where  the  tide  rises  from  30  to  50  feet. 

On  the  other  hand,  where  bays  broaden  out,  bag-shaped,  the 
tidal  range  is  greatly  diminished.  For  instance,  the  Atlantic 
tide,  passing  through  the  Straits  of  Gibraltar,  produces  practi- 
cally no  effect  on  the  broad  Mediterranean ;  but  a  very  small  local 
tide  is  developed  in  the  Mediterranean  itself.  This  almost  com- 
plete absence  of  tide  in  the  Mediterranean  was  of  great  impor- 


18b 


NEW  PHYSICAL  GEOGRAPHY, 


tance  in  the  development  of 
navigation  in  that  inclosed 
sea  (p.  377)  and  the  growth 
of  nations  along  its  shores. 
With  strong  tidal  currents 
to  battle  against,  the  move- 
ment of  their  small,  open 
boats,  propelled  by  oars, 
would  have  become  a  much 
more  difficult  task. 

Along  irregular  coasts 
there  are  bays  where  th^ 
tidal  range  is  greater  than 
in  neighboring  parts  of  the 
coast.  If  there  happens  to 
be  connection  between  two 
such  places,  rapid  tidal  cur- 
rents, or  races,  will  pass 
through  the  connecting 
straits.  An  illustration  of 
this  is  found  in  southern 
Massachusetts,  where  rapid 

currents  flow  between  Buzzards  Bay  and  Vineyard  Sound  (Fig. 

332).    A  similar  current  occurs  at  Hell  Gate,  in  the  narrow  strait 

between  New  York  Bay  and  Long  Island  Sound  (Figs.  333,  334). 
On  entering  some  river  mouths  the  tidal  current  changes  to  a 

wave,  known  as  the 

^>?-e  (Fig.  323),  which 

travels    rapidly    up- 
stream.    It  is  found 

ill  the  Seine,  Severn, 

Amazon,  and  several 

other  rivers. 

Not  only  does  the 

tide  vary  from  place 

to    place,    but    also 

from    time   to  time. 

At    new    and    full 


.B0RM>Y<1  CO,,  N.Y. 

Fig.  332.  —  Range  of  tide,  south  of  Cape  Cod, 
indicated  by  figures.  In  Buzzards  Bay 
it  rises  4.1  feet ;  in  Vineyard  Sound,  from 
1.5  to  3.1;  consequently  rapid  currents, 
or  races,  pass  through  gaps  between  the 
islands  that  separate  the  two  bodies  of 
water. 


aORMAY  t  CO.,   N.Y. 


Fig.  333. —  The  height  to  which  the  tide  rises  on 
the  two  sides  of  Hell  Gate,  over  which  there  are 
rapid  tidal  currents 


THE  OCEAN. 


189 


moon  the  tidal  range  is  greater  than  during  the  quarters.  Tides 
with  high  range  are  known  as  spring  tides,  those  with  low  range, 
neap  tides  (Appendix  E).  The  correspondence  of  spring  and  neap 
tides  to  phases  of  the  moon,  and  the  fact  that  two  complete 
tides  occur  every  24  hours,  52  minutes  (the  period  between  two 
moonrises),  long  ago  led 
to  the  discovery  that  the 
tides  are  due  to  some  in- 
fluence of  the  moon. 

Tides  are  of  great  im- 
portance along  the  coast. 
The  tidal  currents  drift 
sediment  about,  thus 
helping  to  form  sedi- 
mentary strata  (p.  32). 
They  also  deposit  sedi- 
ment in  harbors,  and 
each  year  large  appro- 
priations are  necessary 
for  the  purpose  of  re- 
moving such  deposits. 
By  these  currents,  too,  a 
circulation  is  caused  in 
harbors  (Fig.  330),  thus 
helping  to  remove  the  filth  that  necessarily  finds  its  way  into 
the  ocean  near  large  cities. 

Tidal  currents  aid  or  impede  vessels,  according  to  their 
direction  ;  and  they  sometimes  drift  vessels  from  their  course, 
placing  them  in  dangerous  positions.  Every  now  and  then 
in  foggy  weather,  when  the  land  cannot  be  seen,  vessels  run 
aground,  because  the  tide  has  drifted  them  out  of  their  course. 
The  captains  of  all  large  ships  carry  tide  tables  and  charts 
to  aid  them  in  navigation.  One  use  of  these  is  to  tell 
when  the  tide  is  high,  for  the  entrances  to  many  harbors  are 
too  shallow  to  admit  large  ships  at  low  tide. 


HOURS  AFTER  TRANSIT 
III      IV      V      VI     VII    VIII    IX      X       XI       0 

1     It     III 

111 

X 

X 

3 

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N 

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\ 

2 

r 

-^ 

\ 

/ 

\ 

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4 

1 

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^^ 

\ 

\ 

0 

A 

ii 

1 

\ 

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J 

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\ 

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1 

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k 

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\ 

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X 

f 

k 

V 

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2 

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i 

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V 

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K. 

V 

r-> 

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3 

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x. 

^ 

Fig.  334.  —  Diagram  to  show  time  of  arrival 
and  height  reached  by  the  tides  on  the  two 
sides  of  Hell  Gate.  The  currents  at  Hell 
Gate  are  therefore  due  to  two  causes  . 
(1)  the  time  of  high  tide  differs  on  the 
two  sides ;  (2)  the  tidal  range  differs. 


190 


NEW  PHYSICAL   GEOGRAPHY, 


Summary.  —  Every  12  hours,  26  minutes,  the  ocean  surface 
rises  and  falls  with  the  passage  of  a  tidal  wave.  In  the  open  ocean  the 
range  is  afoot  or  tivo;  along  the  coast  from  3  to  10  feet;  in  ^ -shaped 
bays  even  30  to  50  feet;  but  in  large  bays  that  broaden,  the  tide  may 
be  destroyed.     Along  irregular  coasts  the  rise  and  fall  of  the  tide 

cause  currents,  which  may 
become  very  rapid  races. 
Tidal  currents  move  sedi- 
ment about,  helping  to  de- 
posit sedimentary  strata; 
they  drifi  sediment  into  har- 
bors; they  keep  the  harbor 
water  in  circidation;  they 
aid  or  impede  navigation; 
and  they  sometimes  place  ves- 
sels in  dangerous  positions. 

136.  Ocean  Currents.  — 
The  ocean  waters  are  in 
constant  Circulation,  not 
only  along  the  bottom 
(p.  184),  but  also  in  well- 
defined  surface  currents 
(Fig.  335).  The  exists 
ence  of  ocean  currents  has 
been  known  for  a  long 
time;  indeed,  Columbus 
noticed  them  along  the 
American  coast,  and  Ben- 
jamin Franklin  studied  them  and  considered  them  the  result  of 
steadily  blowing  winds.  It  is  now  known  that  there  are  cur- 
rents slowly  sweeping  through  each  of  the  oceans  (Fig.  338). 

Differences  in  temperature  of  the  ocean  water  account  for 
the  settling  of  water  in  cold  regions  and  its  circulation 
along  the  sea  bottom  (p.  184).  But  it  does  not  seem  an 
adequate  explanation  for  the  surface  currents* 


Fig.   335.  —  The  drifting  of  a  wreck  from 

March  13,  1888,  till  't  went  ashore  Janu- 

*  ary  25, 1889.     Storm  winds  now  and  then 

caused  the  wreck  to  leave  its  general 

course  in  the  ocean  drift. 


THE    OCEAN. 


191 


CHAR'^   OF  THE 

GULF  STREAM, 

SHOWING   ITS  AXIS 
AND   LIMITS 

Washington 


New  Yorkf 


Boston  1   ^    ,^     _   , 
^Cape  Cod 

'  aNANTCCKBT; 
•  BLOCK  I.      '•       /' 


The  explanation  that  best  accounts  for  surface  currents  is 
the  effect  of  steadily  blowing  winds,  as  suggested  by  Franklin. 
By  blowing  on  a  pan  of  water  with  sawdust  floating  in  it, 
a  drift  of  water  is  seen  to  start;  in  like  manner,  winds  blow- 
ing over  lakes  or  ocean  start  a  similar  drift  of  surface  water. 
Such  wind-drift  currents  continue  to  move  for  some  time 
after  the  wind  dies  down. 

A  comparison  of  the  ocean- 
current  chart  (Fig.  338)  and 
the  wind  chart  (Fig.  408) 
shows  that  there  is  a  close 
resemblance  between  the 
direction  of  ocean  currents 
and  regular  winds.  We  will 
study  the  currents  of  the 
Atlantic  Ocean  to  see  how 
close  this  relationship  is. 

In  the  equatorial  region 
there  is  a  drift^  of  water, 
the  Equatorial  Drifts  toward 
the  South  American  coast. 
At  the  angle  of  South  Amer- 
ica it  divides,  the  smaller 
portion  going  into  the  South 

Atlantic,  the  larger  into  the  North  Atlantic.  This  Equato- 
rial Drift  is  exactly  what  we  would  expect  to  find,  for  the 
northeast  and  southeast  trade  winds  blow  steadily  day  after 
day,  drifting  the  water  westward  before  them. 

After  dividing  on  the  coast  of  South  America,  the  drift 
follows  the  coast  for  a  while,  then  slowly  swings  to  the  right 
in  the  northern  hemisphere,  and  to  the  left  in  the  southern. ^ 

1  A  slow  current  may  be  called  a  drift,  a  more  rapid  current  a  stream. 

2  This  swinging  is  caused  by  the  effect  of  the  earth's  rotation,  which 
deflects  all  moving  bodies,  whether  wind  or  water  currents,  from  a  straight 
course.  In  the  northern  hemisphere  the  moving  body  is  turned  to  the  rights 
in  the  southern  hemisphere  to  the  left. 


Joc;=>y    BAHAMA 
fCape  Florida 


ISLANDS 


•0 


ajRMAY    i    CO.,    N.Y 


Fig.  336.— The  Gulf  Stream. 


192 


NEW   PHYSICAL    GEOGRAPHY. 


Thus  a  great,  slowly  moving  eddy  is  formed  in  each  ocean. 
Floating  seaweed  (^Sargassum)  accumulates  in  the  center  oi 
the  eddy  in  such  abundance  that  it  has  been  called  the 
GrassT/,  or  Sargasso^  Sea.  Columbus  encountered  it,  and 
his  sailors,  not  knowing  what  it  was,  feared  tliat  the  ships 
would  run  aground  in  it. 

A  portion  of  the  North  Equatorial  Drift  enters  tlie  Caribbean 
Sea,  part  coming  out  between  the  West  Indies,  part  continuing 

on  into  the  Gulf  of 
Mexico  (Fig.  337). 
The  portion  that  en- 
ters the  Gulf  is 
warmed  still  more  in 
that  inclosed  sea.  and 
escapes,  b  e  t  vv^  e  e  n 
Cuba  and  Florida,  as 
a  narrow  and  rapidly 
moving  stream  of 
warm  water,  known 
as  the  G-ulf  Stream 
(Figs.  336,33'").  On 
the  Florida  coast  it 
has  a  velocity  of  4  or 
5  miles  an  hour.  The 
Gulf  Stream  rapidly 
broadens,  a  part  of  it 
joining  the  great 
North  Atlantic  Eddi' 
that  circles  in  the 
open  ocean  outside 
of  the  West  Indies.  This  portion  returns  to  once  more  form 
a  part  of  the  Equatorial  Drift. 

A  smaller  portion  of  the  Gulf  Stream  water,  and  some  of 
the  North  Atlantic  Eddy,  drifts  on  into  the  region  of  the 
west  winds,  which  drive  it  on  toward  the  coast  of  northern 


Fig.  337. —  Diagram  to  show  the  currents  of  the 
western  North  Atlantic.  Figures  tell  rate  of 
movement  in  miles  per  hour. 


THE  OCEAN^  193 

Europe,  as  the  West  Whid  Drift.  Thus  water,  warmed  in 
the  equatorial  regioji,  tlie  Caribbean  Sea,  and  the  Gulf  of 
Mexico,  is  carried  to  the  European  coast,  and  even  into  the 
Arctic.  There  is  no  similar  stream  in  the  South  Atlantic, 
because  there  are  no  partly  closed  seas  for  the  drift  to  enter. 

Study  the  currents  of  the  Pacific  to  see  if  the  same  great  eddies 
are  found  there.  Notice  that  in  the  Southern  Ocean,  where  there 
are  no  continents  to  turn  the  currents,  the  West  Wind  Drift  ex- 
tends 'Completely  around  the  globe. 

Besides  these  eddies,  there  are  special  currents,  one  of  which,  the 
Labrador  Current,  is  of  great  importance  to  America.  This  is  a 
cold  current,  descending  from  among  the  islands  of  the  Arctic 
along  the  Labrador,  Newfoundland,  and  New  England  coasts  (Fig. 
337).  It  keeps  close  to  the  American  shores,  being  turned  to  the 
right  by  the  influence  of  rotation.  Thus,  while  warm  water  is 
drifted  toward  Europe,  cold  water  flows  down  the  American  coast 
as  far  south  as  Cape  Cod,  where  it  disappears  by  settling  and 
mingling  with  the  warm  water. 

Summary.  —  The  surface  currents  are  due  to  the  drifting  of  water 
before  steadily  blowing  ivinds.  In  each  ocean  there  are  great  eddies, 
started  by  the  trade  winds,  which  cause  an  Equatorial  Drift  toward 
the  west.  This,  dividing  on  the  continents,  follows  the  coast  north- 
ward and  southward  for  a  ivhile  ;  then  it  is  turned,  by  the  effect  of 
rotation,  to  the  right  in  the  northern  hemisphere  and  to  the  left  in  the 
southern.  TJius  an  eddy  is  caused  in  each  ocean,  both  north  and 
south  of  the  equator.  A  x>art  of  the  North  Equatorial  Drift  enters 
the  Gulf  of  Mexico  and  emerges  as  the  ivarm  Gulf  Stream,  a  j)or- 
tion  of  ichich  joins  the  eddy  of  the  North  Atlantic.  A  portion  of  the 
eddy,  and  of  the  Gulf  Stream,  is  drifted  by  the  west  ivinds  to  the  Euro- 
pean coast,  and  even  into  the  Arctic.  In  the  southern  hemisphere  the 
West  Wind  Drift  extends  around  the  earth.  The  cold  Labrador 
Current  sweeps  down  the  American  coast  from  the  Arctic,  and,  being 
turned  to  the  right,  is  forced  to  hug  the  coast  till  it  sinks. 

137.    Effects  of  Ocean  Currents.  —  The  most  important  ef- 
fect of  ocean  currents  is  on  climate  (p.  2T8^,     For  instance, 
o 


194  NEW  PHYSICAL   GEOGRAPHY. 

the  warm  water  that  is  borne  into  the  Arctic  by  the  West 
Wind  Drift,  influences  the  temperature  of  northern  Europe. 
Its  effect  was  very  well  shown  by  Nansen's  voyage  toward 
the  pole.  He  started  into  the  Arctic  north  of  Scandinavia, 
where  the  warm  drift  keeps  the  sea  fairly  clear  of  ice  in 
summer  (Fig.  338),  and  was  able  to  push  his  ship  far  into 
the  Arctic  before  he  met  with  impassable  ice. 

Ocean  currents  aid  or  retard  vessels,  according  to  their 
direction ;  and,  in  their  reckonings,  navigators  must  .make 
allowance  for  this  influence.  Columbus  had  much  difficulty 
in  navigating  his  small  ships  among  the  currents  along  the 
northern  coast  of  South  America.  Currents  have  other  im- 
portant influences,  for  example,  causing  fogs  (p.  247),  drift- 
ing sea  ice  and  icebergs,  and  bringing  oxygen  and  food  for 
many  sea  animals  (pp.  196,  197). 

Summary.  —  Ocean  currents  affect  climate,  influence  the  movemrent 
of  vessels,  and  are  further  important  in  causing  fogs,  drifting  sea  ice 
and  icebergs,  and  bearing  oxygen  and  food  for  sea  animals.   ' 

138.  Ice  in  the  Ocean.  —  Each  winter  a  large  part  of  the  Arctic 
Ocean  is  frozen  over,  often  to  a  depth  of  5  or  10  feet.  The  tidal 
currents  move  the  ice  about,  opening  cracks  or  leads,  and  closing 
them  again  with  so  irresistible  a  force  that  the  ice  is  broken  and 
piled  up  in  ridges  of  pack  ice  often  50  or  100  feet  high.  More  than 
one  Arctic  ship  has  been  crushed  like  an  eggshell  between  these 
moving  ice  fields. 

Nansen,  Abruzzi,  and  Peary  have  all  tried  to  reach  the  North 
Pole  ov^r  this  frozen  sea ;  but  the  many  leads,  and  the  irregular 
surface  of  the  ice  packs,  have  proved  such  barriers  to  progress 
that  no  one  has  yet  succeeded  in  reaching  the  pole. 

In  summer  tne  ice  breaks  up,  and  the  fragments  drift  south- 
ward till  they  melt.  Each  spring  and  early  summer  there  is  a 
steady  stream  of  these  ice  fragments,  or  icefloes,  passing  down  the 
Labrador  coast  in  the  Labrador  current  (Fig.  340). 

Icebergs,  discharged  from  the  ice  sheets  of  Greenland  and  other 
northern  islands  (p.  145),  also  drift  in  the  Arctic  waters  (Fig.  339). 
They  are  huge  floating  islands  of  ice,  sometimes  rising  more  than 


^s 


k^^-:^^$^$s4$^^^V^^^ 


Fig.  339.  —  Glacier  ice  in  Greenland  (near  Fig.  264),  the  Cornell  glacier  beinj' 
directly  opposite.    The  ice  cliff,  Fig  265,  is  just  over  the  boat. 


Fig.  340. Sea  loe  in  sninmer  in  the  Labrador  Current  off  the  coast  of  BaflBn 

Land.    The  ship  was  held  here  for  several  days,  then  the  ice  was  opened  by 
tidal  currents  and  the  ship  was  able  to  leave. 


THE  OCEAN.  195 

100  feet  above  the  water.  Since  ice  floating  m  salt  water  has  about 
seven  parts  below  water  to  one  above,  some  of  these  bergs  extend 
700  or  800  feet  beneath  the  surface.  They  frequently  run  aground 
(Fig.  267),  either  breaking  to  pieces  by  the  shock,  or  remaining 
aground  till  melting  allows  them  to  float  away.  So  huge  are  these 
bergs  that,  before  melting  entirely,  'chey  may  travel  1000  or  2000 
miles,  even  down  to  the  path  followed  by  ocean  liners.  They 
are  much  dreaded,  for  even  the  largest, ship  may  be  destroyed  by 
running  into  one. 

Far  greater  icebergs  are  discharged  from  the  Antarctic  ice  sheet, 
some  of  them  rising  500  feet  above  the  water  and,  consequently, 
measuring  three  quarters  of  a  mile  from  base  to  top.  They  have 
steep  sides  and  flat  tops,  and  are  sometimes  several  miles  long. 

Summary.  —  Tlie  Arctic  sea-ice,  formed  in  ivinter,  breaks  up  in 
summer,  some  of  it  drifting  southivard  in  the  Labrador  current. 
Huge  icebergs,  discharged  froyn  the  Greenland  ice  sheet,  drift  in  the 
Arctic,  and  still  larger  ones  in  the  Antarctic. 

LIFE  IN   THE   OCEAN. 

139.  Surface  (Pelagic)  Life.  —  The  abundance  of  life  in 
the  ocean  is  marvelous.  A  pail  of  water  dipped  from 
the  surface  will  contain  thousands  of  individuals,  mostly 
microscopic.  These  organisms  are  drifted  about  by  winds 
and  currents,  and  with  them  are  many  larger  forms,  some 
merely  floating,  some  swimming.  Pieces  of  floating  wood 
have  animals  attached  to  them;  and  in  the  floating  seaweed, 
many  animals  live  in  little  worlds  of  their  own. 

The  minute  organisms  are  the  source  of  food  for  many 
larger  animals,  even  for  the  huge  whales.  Swimming  with  its 
mouth  open,  the  whale  strains  the  water  to  obtain  its  food,  and 
thus  the  largest  of  animals  feeds  upon  the  smallest. 

Among  the  many  fishes  are  some,  like  the  mackerel,  which 
are  valuable  for  food  supply.  For  protection,  the  mackerel 
and  some  other  fishes  swim  together  in  vast  numbei's,  forming 
"scbov*\s"  or  "shoals," 


196 


NEW  PHYSICAL   GEOGRAPHY. 


Summary.  —  Life  is  very  abundant  in  the  surface  waters,  both 
large  and  microscopic  forms  being  present,  the  latter  serving  as  a 
food  supply  for  even  the  largest  of  animals,  the  whale. 

140.  Life  along  Coasts  (Littoral). — Along  the  coast  line 
there  is  also  abundant  animal  life ;  but  it  is  more  varied 
than  in  the  open  ocean,  because  the  coast  offers  so  many 
different  conditions.  Some  of  the  littoral  animals  swim  in 
the  surf ;  others  cling  to  the  rocky  coast ;  and  others  bur- 
row in  the  sand  or  mud.  Many  kinds,  such  as  clams,  oysters, 
lobsters,  and  a  large  number  of  fishes,  are  valuable  as  food ; 
others,  such  as  sponges,  precious  corals,  and  pearls,  are  of 
value  for  other  purposes. 

Plants,  as  well  as  animals,  abound  on  the  seacoast.  This  is 
true  in  the  mangrove  swamps  of  the  tropical  zone  (Fig.  379)  and 
the  salt  marshes  of  the  temperate  zones  (Fig.  378) ;  it  is  also  true 

of  rocky  coasts,  to 
which  seaweeds 
cling,  covering  the 
rock  with  a  mat  of 
plant  growth  (Fig. 
331). 

Some  conditions 
are  unfavorable  to 
littoral  life ;  for 
example,  (1)  fre- 
quent earthquake 
shocks,  (2)  the 
grinding  of  Arctic 
sea-ice,  and  (3)  the 
grinding  of  moving 
sand  and  pebbles 
on  the  beaches. 
Other  conditions  are  very  favorable,  especially  the  presence  of 
food-bringing  currents.  Few  parts  of  the  earth  have  such  an 
abundance  and  variety  of  animal  life  as  the  coral  reefs  (Fig.  380), 
which,  are  bathed  by  warm  ocean  currents. 


Fig.  341. 


A  Gloucester  fishing:  schooner  anchored  on 
the  Fishing  Banks. 


THE  OCEAN.  197 

The  influence  of  food-briuging  currents  is  felt  on  those  shallow 
Danks,  known  SiS  JisJmig  banks,  where  large  numbers  of  food  fish 
live.  This  is  well  illustrated  on  the  fishing  banks  off  northeastern 
America,  such  as  Georges  and  the  Grand  Banks  of  Newfoundland, 
which  are  bathed  by  the  Labrador  current.  These  are  resorted 
to  for  cod,  haddock,  and  halibut  by  fishing  vessels  from  France, 
Newfoundland,  Nova  Scotia,  and  many  New  England  ports,  espe- 
cially Gloucester,  Mass.  From  a  passing  ocean  liner,  the  schooners 
may  be  seen  at  anchor  in  the  open  ocean  (Fig.  341),  the  men  busily 
fishing,  either  from  the  sides  of  the  vessel  or  from  small,  open  dories. 
It  is  a  hazardous  calling,  and  many  a  fishing  vessel  has  been  sunk 
during  the  fierce  storms,  or  crushed  by  the  huge  transatlantic  liners. 
Every  year,  also,  men  in  dories  are  separated  froju  their  vessels  dur- 
ing fogs,  which  are  frequent  on  the  banks.  They  then  drift  about 
in  the  open  ocean,  often  until  they  starve,  or  freeze,  or  founder. 

Summary.  —  Animal  life  along  the  coast  is  abundant  and  varied  ; 
there  is  also  much  plant  life.  Food-bringing  ciirrents  especially 
favor  life,  as  is  illustrated  on  coral  reefs  and  fishing  banks,  from, 
which  valuable  food  fish  are  obtained. 

141.  Life  on  the  Ocean  Bottom  (Abyssal).  —  Absence  of  sun- 
light prevents  the  existence  of  plant  life  in  the  deep  sea ;  but, 
even  at  depths  of  two  or  three  miles,  there  are  animals  on  the 
ocean  bottom  (p.  174).  These  animals  live  in  darkness,  in 
water  almost  at  the 
freezing  point,  and 
under  a  pressure  of 
many  tons. 

The  conditions  on 
the      ocean      bottom  Fig.  342.  —  A  deep-sea  fish, 

are    very    uniform : 

summer  and  winter  are  alike ;  day  and  night  are  dark ;  every- 
where it  is  cold ;  and  the  sea  floor  is  a  monotonous  expanse  of 
ooze  or  clay.  The  nature  of  animal  life  varies  with  the  depth 
because  of  differences  in  temperature ;  and  where  the  water  is  very 
cold,  animals  are  scarce  and  have  little  vitality.     The  supply  of 


198 


NEW  PUYSICAZ    GEOGRAPHY, 


Fig.  343.  —  A  stalked  crinoid    from  tlie 
deep  sea. 


oxygen,  brought  by  the  slowly 
moving  bottom  current  (p.  184), 
and  the  supply  of  food,  which 
settles  down  to  the  bottom  as 
organisms  at  the  surface  die 
and  slowly  sink,  also  limit 
abyssal  life. 

Under  such  uniform  con- 
ditions it  is  not  strange  that 
many  peculiar  forms  of  animal 
life  should  be  found  in  the 
deep  sea.  Some  of  them,  like 
the  stalked  crinoids  (Fig.  343), 
belong  to  types  once  abundant, 
but  now  living  only  on  the. 
ocean  bottom.  There  they  havb 
been  able  to  survive,  as  in  an 
asylum,  while  those  which  were 
out  in  the  world,  and  exposed 
to  the  struggle  that  goes  on 
there,  have  been  exterminated. 


Summary.  —  There  is  ivonderfal  uniformity  of  conditions  in  the 
deep  sea,  in  tcMch  animals,  but  no  plants,  live.     The  abundance  and 
distribution  of  ayiimal  life  are  influenced  mainly  by  temperature 
oxygen  supply,  and  food  supply. 


Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  — 124.  Oceanography. — -Definition;  exploring  ex- 
peditions; cables;  sounding ;,  water  samples;  ocean-bottom  nmd:  tem- 
perature; dredging. 

125.  Ocean  Basins.  —  General  condition  ;  deep-sea  plains;  deeps;  eleva- 
tions; Atlantic,  —  deepest  point,  volcanoes,  mid-Atlantic  ridge;  Pacific, 
—  volcanic  chains,  deepest  point,  other  deeps;  Arctic;  Southern  Ocean. 

126.  Deposits  on. the  Ocean  Bottom.  —  (A)  Rock  fragments:  source; 
deposit ;  fossils.  (B)  Ocean-bottom  oozes :  absence  of  rock  waste ;  area 
of  ooze ;  materials  in  ooze  ;  source  of  organisms ;  globigerina  ooze ;  ptero- 
pod  ooze ;  diatom  ooze.  (C)  Red  clay :  solution  of  shells ;  insoluble  parts; 
red  color;  slowness  of  accumulation  ;  proofs- 


THE  OCEAN,  199 

127.  Land  and  Ocean-bottom  Topography.  —  Mountain  folding  and 
volcanic  action;  erosion;  sediment;  result  of  differences. 

128.  Surface  of  the  Sea.  —  Sea  level;  effect  of  continents;  of  winds 
and  storms;  of  deposit  of  sediment ;  of  sinking  ocean  bottom. 

129.  Composition  of  Sea  Water.  —  Original  condition;  increase  in 
saltness;  proportion  of  salt;  other  mineral  substances ;  amount  of  salt ; 
importance;  carbonate  of  lime  ;  presence  of  air ;  importance. 

130.  Density  and  Pressure  of  Sea  Water.  —  {a)  Density :  average 
density;  effect  of  fresh  water;  of  evaporation,  (b)  Pressure:  amount; 
reason  for  no  effect  on  animals;  animals  brought  to  the  surface;  density 
of  ocean-bottom  water. 

131.  Color  and  Light. —  (a)  Color:  entrance  of  sunlight ;  blue  color; 
green  color ;  Yellow  River ;  Red  Sea.  (h)  Light :  darkness  of  ocean 
bottom  ;  blind  fish  ;  phosphorescence  on  ocean  bottom ;  at  the  surface. 

132.  Temperature  of  the  Oceans.  —  From  tropical  to  frigid  zones; 
inclosed  seas;  decrease  downward;  ocean  bottom  ;  cooling  of  fresh  and 
saltwater;  circulation;  effect  on  animals ;  inclosed  sea  bottoms. 

133.  Wind  Waves.  —  Cause;  nature  of  movement;  height;  crest; 
trough;  whitecaps  ;  rate  of  movement;  effects  on  vessels;  use  of  oil; 
rollers ;  breakers ;  undertow ;  movement  of  rock  fragments. 

134.  Other  Waves.  —  Earthquake  waves, — cause,  size,  effects,  occur- 
rence, distance  of  travel;  iceberg  waves;  hurricane  waves. 

135.  Tides.  —  (a)  Nature  of  tides:  time  of  passage;  tidal  range; 
increase  on  coast;  movement  in  open  ocean;  currents  on  coast;  flow; 
ebb.  (h)  Influence  of  coast:  ordinary  range;  effect  of  V-shaped  bays; 
of  broadening  bays;  Mediterranean;  races;  examples;  bore,  (c)  Influ- 
ence of  moon's  phases:  spring  tides;  neap  tides;  relation  of  tides  to 
moon,  (fl)  Effects  of  tides  :  on  deposit  of  strata  ;  on  deposits  in  harbors ; 
on  circulation  of  water  in  harbors  ;  on  navigation. 

136.  Ocean  Currents.  —  Early  knowledge  ;  effect  of  temperature  differ- 
ences ;  of  steady  winds ;  resemblance  between  winds  and  currents  ;  a  drift ; 
a  stream;  Equatorial  Drift;  effect  of  continents;  effect  of  rotation  ;  Sar- 
gasso Sea;  Gulf  Stream;  North  Atlantic  Eddy;  West  Wind  Drift; 
Pacific  eddies ;  West  Wind  Drift  of  Southern  Ocean ;  Labrador  Current ; 
compare  European  and  American  coasts. 

137.  Effects  of  Ocean  Currents.  —  Climate;  sunsen's  journey;  effect 
on  navigation ;  fog ;  ice  ;  oxygen  and  food. 

138.  Ice  in  the  Ocean.  —  (a)  Sea  ice:  depth;  leads;  pack  ice;  travel 
over  the  ice  ;  ice  floes,  (h)  Icebergs  :  source ;  size ;  grounding ;  distance 
traveled ;  Antarctic  bergs. 

139.  Surface   (Pelagic)   Life.  —  Abundance;  modes  of  life;  whalef^ 
mackerel. 


200  NEW  PHYSICAL   GEOGRAPHY. 

140.  Life  along  Coasts  (Littoral).  —  Varied  conditions ;  valuable  ani- 
mals; plant  life;  unfavorable  conditions;  favorable  conditions;  fishing 
banks,  —  location,  food  fish,  fishing,  dangers. 

141.  Life  on  the  Ocean  Bottom  (Abyssal).  —  Plants;  animals;  sur- 
roundings ;  temperature  ;  oxygen  ;  food  ;  survival  of  types. 

Questions.  — 123.   In  what  ways  is  the  ocean  of  importance? 

124.  What  is  oceanography?  What  expeditions  have  been  engaged 
in  deep-sea  exploration  ?  How  is  the  depth  of  the  sea  learned  ?  What 
facts  are  learned  during  a  sounding?     How  is  dredging  carried  on? 

125.  What  is  the  condition  of  the  ocean  bottom  ?  What  irregularities 
occur  ?  What  irregularities  are  found  in  the  Atlantic  ?  In  the  Pacific  ? 
What  is  known  of  the  Arctic  and  Southern  oceans  ? 

126.  (A)  What  is  the  nature  of  the  deposit  near  the  coast?  (B)  Why 
is  ooze  deposited  far  from  land?  Of  what  is  it  composed?  (C)  What  is 
the  origin  of  red  clay  ?     Prove  that  it  is  forming  slowly. 

127.  Why  are  land  and  ocean-bottom  topography  different? 

128.  What  is  sea  level ?    How  is  this  level  changed? 

129.  What  is  the  origin  of  the  mineral  substances  in  sea  water? 
What  mineral  substances  are  there?  How  much  salt  is  there?  Of 
what  importance  is  the  carbonate  of  lime ?    The  air? 

130.  What  causes  water  to  vary  in  density  ?  What  is  the  pressure  or. 
the  ocean  bottom?  Why  do  not  animals  feel  it?  What  would  be  the 
condition  if  the  ocean-bottom  water  were  compressed  like  the  air  ? 

131.  What  causes  are  there  for  the  different  colors  of  the  ocean? 
What  light  is  there  on  the  ocean  bottom? 

132.  What  causes  differences  in  temperature  of  the  ocean-surface 
waters?  What  are  the  temperature  conditions  below  the  surface?  Why 
is  the  bottom  temperature  lower  than  that  in  lakes  ?  What  is  the  cause 
of  the  slow  circulation  ?     What  proof  is  there  of  it? 

133.  What  causes  waves  ?  What  is  the  real  movement  of  the  water  ? 
What  causes  whitecaps?  How  high  may  waves  be?  How  fast  may 
they  move?  What  damage  may  they  do  to  ships?  How  may  this  dan- 
ger be  lessened  ?  What  is  the  cause  of  rollers?  What  causes  breakers? 
What  is  undertow  ?     How  are  rock  fragments  carried  away  ? 

134.  What  causes  earthquake  waves  ?  What  are  some  of  their  effects  ? 
What  other  causes  are  there  for  waves  ? 

13.5.  To  what  height  does  the  tidal  wave  rise?  Under  what  condi- 
tions are  tidal  currents  formed?  What  is  flow?  Ebb?  What  happens 
as  tides  enter  narrowing  bays?  Where  they  enter  broadening  bays? 
Give  an  illustration.  What  causes  tidal  races?  Give  illustrations. 
What  is  the  bore?  What  reasons  are  there  for  connecting  tides  with  the 
moon  ?    Name  some  important  effects  of  tides. 


THE  OCEAN.  201 

136.  What  early  knowledge  of  ocean  currents  was  there  ?  What  effect 
have  differences  in  temperature  on  ocean  movements?  What  effect  has 
the  wind?  Describe  the  system  of  currents  in  the  Atlantic  Ocean,  and 
show  how  it  is  related  to  winds.  Describe  and  explain  the  Gulf  Stream. 
What  is  the  Sargasso  Sea?  What  currents  are  found  in  the  Pacific? 
Other  oceans  (Fig.  338)  ?     Describe  the  Labrador  Current. 

137.  Name  the  important  effects  of  ocean  currents. 

138.  What  are  the  characteristics  of  sea  ice  ?  Describe  the  icebergs 
of  the  Arctic.     Of  the  Antarctic. 

139.  What  are  the  conditions  of  pelagic  life  ? 

140.  How  do  the  conditions  surrounding  littoral  life  vary?  In  what 
situations  are  littoral  plants  found?  What  conditions  oppose  littoral 
life?  What  conditions  favor  it?  Why  are  fishing  banks  the  home  of 
food  fish  ?     What  dangers  accompany  the  fishing  ? 

141.  What  conditions  influence  life  on  the  ocean  bottom  ? 
Suggestions.  —  (1)  Prove  that  salt  water  is  more  dense  than  fresh,  by 

putting  shot  in  a  bottle  until  it  will  barely  sink  in  fresh  water,  taking 
care  to  cork  it;  then  dissolve  salt  in  the  water  and  again  put  the  bottle  in 
it.  (2)  Cut  a  cube  of  ice  and  place  it  in  fresh  water.  Measure  the 
amount  above  and  below  water.  Place  it  in  salt  water  and  measure 
again.  What  is  the  result?  (3)  In  a  large  pan,  or  tub,  of  water  place  a 
bottle,  partly  submerged.  Start  waves  by  blowing  on  one  end.  Note  how 
they  travel  beyond  their  source.  Note  the  movements  of  the  bottle  as 
the  waves  pass  under  it.  Have  the  students  describe  its  movements.  At 
one  end  of  the  pan  make  a  shelving  beach  of  sand,  with  a  cliff  at  one  end. 
Observe  and  describe  the  action  of  the  M^aves  as  they  approach  the  shore. 
What  differences  are  there  in  the  behavior  of  the  waves  on  the  beach  and 
on  the  cliff  ?  Are  fragments  removed  ?  AVhere  do  they  go  ?  Make  waves 
that  advance  diagonally  on  the  shore  and  observe  the  movement  of  the 
fragments.  To  see  this  clearly,  place  at  one  point  some  colored  objects, 
like  bits  of  colored  glass,  and  note  how  they  move.  (4)  In  the  pan  build 
a  coast,  roughly,  like  that  of  North  and  South  America.  Sprinkle  saw- 
dust on  the  water  and  blow  over  its  surface  from  both  sides  of  a  line 
(the  equator),  to  imitate  the  trade  winds  approaching  the  equator. 
Watch  the  drift  of  water.  Do  you  see  any  resemblance  to  the  ocean- 
current  systems  of  the  Atlantic?  (5)  Take  the  temperature  at  the 
bottom  of  the  pan  near  the  middle  line,  then  place  ice  in  the  water  as  far 
away  from  the  middle  as  possible.  Be  careful  not  to  stir  the  water. 
After  the  ice  has  melted,  again  take  the  temperature  under  the  middle 
line.  What  is  the  difference?  It  would  be  possible  also  to  imitate  the 
conditions  in  the  Gulf  of  Mexico  (p.  184).  (6)  If  the  school  is  by  the 
sea,  or  even  near  a  lake  or  pond,  waves  and  wind-formed  currents  should 


202  NEW  PHYSICAL   GEOGRAPHY, 

be  studied.  Note  their  force,  form,  and  effects.  (7)  If  by  the  seashore, 
the  tides  should  be  studied.  Observe  time  of  low  and  high  tides  for 
three  successive  days.  These  facts  may  be  obtained  from  an  almanac, 
or  better,  from  the  Tide  Tables  published  by  the  U.  S.  Coast  Survey  at 
Washington,  the  tables  for  the  year,  for  the  Atlantic  (15  cents)  and  Pa« 
cific  (10  cents)  coasts.  Observe  the  time  of  spring  and  neap  tides.  How  do 
they  compare  with  the  phases  of  the  moon  ?  What  is  the  range  of  the  tide 
in  each  case?  Are  there  any  tidal  currents  near  at  hand  ?  Are  the  tides 
of  any  importance  in  your  harbor?  That  is,  do  they  do  any  harm  oi 
good?  (8)  On  cross-section  paper,  plot  a  curve  to  represent  the  high 
and  low  tide  for  a  month  (obtaining  the  facts  from  the  Tide  Tables). 
Let  each  of  twelve  students  do  a  different  month  and  then  paste  them 
all  together.  Above  the  curves  indicate  each  quarter  of  the  moon. 
Have  the  students  study  these  to  see  how  closely  the  phases  of  the  moon 
coincide  with  variations  in  range  of  the  tide.  Let  the  vertical  side  of 
each  square  represent  a  foot  of  tidal  rise,  and  the  horizontal  side,  threi 
hours  of  time.  (9)  On  an  outline  map  of  the  world  sketch  the  ocean 
currents  from  the  chart  in  the  book  (Fig.  338). 

Reference  Books.  —  Thompson,  Depths  of  the  Sea,  2  vols.,  Macmillan 
Co.,  New  York,  1873,  $7.50 ;  The  Atlantic,  Macmillan  &  Co.,  London,  1877 
(out  of  print)  ;  Agassiz,  Three  Cruises  of  the  Blake,  2  vols.,  Houghton, 
Mifflin  &  Co.,  Boston,  1888,  |8.00;  WihT>,^  Thalassa,  Marcus  Ward  &  Co., 
London,  1877, 12  shillings  ;  Moseley,  Notes  by  a  Naturalist,  Murray,  Lon- 
don, 1892,  9  shillings ;  Sigsbee,  Deep  Sea  Sounding  and  Dredging,  U.  S. 
Coast  Survey,  Washington,  D.C.,  1880;  Tanner,  Deep  Sea  Exploitation, 
p.  1,  1892  Report,  U.  S.  Fish  Commission,  Washington,  D.C. ;  Darwin, 
The  Tides,  Houghton,  Mifflin  &  Co.,  Boston,  1898,  -12.00  ;  Tide  Tables 
for  the  Year,  U.  S.  Coast  Survey,  AVashington,  $0.25 ;  Pillsbury,  The 
Gulf  Stream,  Annual  Repot "",  U.  S.  Coast  Survey  for  1890,  Appendix  10, 
Washington,  D.C. 


CHAPTER   XI. 

SHORE  LINES. 

142.  Importance  of  Shore  Lines.  —  Some  of  the  busiest 
centers  of  human  industry  are  located  on  or  near  the  sea- 
coast.  The  great  and  increasing  trade  that  uses  the  ocean 
as  a  highway  converges  toward  these  centers  ;  and  to  and 
from  them,  by  river,  canal,  and  railway,  there  is  a  steady 
movement  of  goods  for  shipment  or  for  distribution. 

So  important  is  the  coast  line  that  charts  have  been  made 
of  all  parts  of  it  that  are  reached  by  the  vessels  of  commerce. 
Governments  maintain  bureaus,  like  the  United  States  Coast 
Survey,  whose  duty  it  is  to  map  the  coast,  to  determine  by 
accurate  soundings  the  depth  of  water,  and  to  detect  and 
record  all  changes,  such  as  shifting  of  channels,  which  might 
endanger  ships.  In  addition,  our  government  annually 
spends  large  sums  of  money  for  the  improvement  of  har- 
bors. This  money  is  used  in  building  breakwaters  where 
no  natural  harbors  exist ;  in  dredging  out  the  sand  and  mud 
that  waves  and  currents  deposit  ;  and  in  building  jetties  and 
other  structures  to  control  the  deposits  of  sediment  and 
keep  channels  clear. 

The  approach  to  the  coast,  especially  in  times  of  storm  and 
fog,  is  accompanied  by  so  many  dangers  —  from  hidden  reefs, 
islands,  and  projecting  headlands  —  that  all  civilized  nations 
spend  large  smns  in  the  effort  to  lessen  these  perils.  To  warn 
sailors,  or  to  guide  them  into  port,  lighthouses  are  built  on  exposed 
points  and  light-ships  anchored  on  dangerous  shoals ;  and,  on  the 
charts,  the  location  and  characteristics  of  these  lights  are  shown. 
On  approaching  the  coast  at  night,  the  first  sign  of  land  is  the 
gleam  of  the  lighthouse;  and  by  the  color,  brilliancy,  nature  of 

203 


204  NEW  PHYSICAL   GEOGRAPHY. 

flashes,  or  other  device,  the  mariner  knows  his  position.     During 
fogs  and  stormy  weather  a  fog-horn  adds  its  warning  note. 

Specially  trained  pilots  are  licensed  to  guide  ships  into  port; 
and  buoys  are  placed  at  frequent  intervals  to  mark  the  channel. 
Some  of  the  buoys,  placed  over  reefs  or  near  dangerous  currents, 
have  bells  that  are  rung,  or  whistles  that  are  blown,  by  the  rock-, 
ing  of  the  waves,  to  warn  the  sailors  of  danger.  Even  with  all 
these  precautions  vessels  far  too  frequently  run  ashore.  To 
rescue  the  shipwrecked,  life-saving  stations  are  established  at 
frequent  intervals  by  state  and  national  governments;  and  in 
them  men  with  strong  life-boats,  lines,  and  other  life-saving 
apparatus  are  ever  ready  for  the  call  of  distress. 

The  coast  line  has  become  of  importance  to  many  people  as  a 
vacation  resort.  In  summer,  when  the  interior  of  the  country  is 
hot,  the  seacoast  is  cool  and  pleasant ;  there  are  rocky  coasts  to 
scramble  over,  beaches  to  walk  upon,  surf  to  swim  in,  and  boating 
and  fishing  to  enjoy.  Consequently,  tens  of  thousands  of  people 
go  to  the  seashore  for  a  j)art  or  all  of  the  summer. 

Summary.  —  The  seacoast  is  the  site  of  some  of  the  busiest  centers 
of  human  industry.  It  is  so  important  that  it  is  charted;  harbors  are 
built  or  dredged  out;  lighthouses,  buoys,  and  other  learnings  and 
guides  are  placed  along  it;  and  life-saving  stations  are  established. 
The  seacoast  is  also  an  important  summer  resort. 

143.  The  Seacoast  is  ever  changing.  —  Waves  and  cur- 
rents are  vigorously  at  work,  wearing  away  the  land  (Fig.  347) 
and  moving  rock  fragments  to  places  of  deposit ;  and  rivers 
are  ever  pouring  sediment  into  the  sea.  Along  some  coasts 
the  waves  are  cutting  back  the  cliffs  (Fig.  344)  at  the  rate 
of  one  or  two  feet  a  year  (Fig.  358),  as  on  the  outer  shore 
of  Cape  Cod  and  Martha's  Vineyard.  In  other  places,  deposit 
is  building  out  the  coast,  especially  near  river  mouths 
(Fig.  345).  Pisa,  in  the  Middle  Ages  a  seaport,  is  now 
several  miles  inland  on  the  delta  of  the  Arno,  Leghorn  being 
now  the  seaport  for  that  region. 

Change  in  level  of  the  land  (p.  35),  even  though  slight 
in  amount,  produces  a  difference  in  the  form  of  the  coast. 


SHORE  LINES,  205 

A  slight  elevation  brings  cliffs,  beaches,  and  sea-bottom 
plains  (p.  72)  above  the  reach  of  the  waves ;  a  slight 
depression,  allowing  the  sea  to  enter  the  valleys,  entirely 
alters  the  outline  of  the  coast.  An  elevation  or  depression 
that  in  the  interior  would  pass  unnoticed,  causes  such  changes 
in  the  seacoast  that  it  cannot  escape  attention. 

Since  waves  are  ever  at  work,  since  deposits  of  sediment 
are  always  being  made,  and  since  the  earth's  crust  is  con- 
stantly rising  or  falling,  any  study  of  coast  lines  must  be 
largely  aoncerned  with  the  effects  of  such  changes. 

Summary.  —  The  coast  is  being  cut  back  by  the  waves  in  some 
places,  and  built  out  by  deposits  in  others ;  and  many  changes  are 
made  by  rising  or  sinking  of  the  land. 

144.  Elevated  Sea-bottom  Coasts.  —  The  uplift  of  sea  bot- 
toms, forming  coastal  plains  (p.  72),  produces  a  low,  flat, 
straight  coast  line,  not  generally  fitted  for  dense  settlement. 
Such  coasts  are  found  in  southern  United  States,  Yucatan, 
eastern  Central  America,  and  Argentina.  The  land  back  of 
the  coast  is  often  so  level  that  it  is  swampy,  un healthful,  and 
unfitted  for  agriculture. 

In  tropical  lands,  as  in  Central  America  and  Africa,  such  plains 
are  the  seat  of  deadly  malaria.  Being  made  of  soft, •unconsoli- 
dated deposits  of  clay,  sand,  and  gravel,  the  soil  is  often  so  sterile 
as  to  be  unsuited  to  cultivation.  Where  the  soil  is  fertile  and  not 
too  damp,  however,  the  level  plains  make  excellent  agricultural 
land ;  but  the  lack  of  good  harbors  is  a  handicap  to  devel- 
opment. Good  harbors  are  rare,  chiefly  because  the  contact 
of  the  sea  with  a  level  plain  makes  a  straight  coast  with  few 
irregularities. 

If  a  slight  sinking  occurs,  as  has  been  the  case  in  southern 
United  States,  the  sea  enters  the  valleys,  forming  bays  and  har- 
bors ;  but  the  harbors  are  likely  to  be  poor,  because  the  valleys 
of  a  coastal  plain  are  shallow.  Moreover,  the  waves  and  currents, 
working  with  loose  rock  fragments,  quickly  build  sand  bars,  which 
skirt  the  coast,  inclosing  shallow   lagoons,  and  even  extending 


206  NEW  PHYSICAL   GEOGRAPHY. 

across*  tlie  mouths  of  bays  and  harbors  (Figs.  372,  373).  A  con. 
stant  struggle  is,  therefore,  necessary  to  prevent  their  entrances 
from  being  choked  with  sand. 

Summary.  —  Elevated  sea-bottom  plains  are  loc,  level,  straight, 
skirted  by  sand  bars,  and  have  few  harbors,  and  these  mostly  shallow 
and  poor,  even  ivhere  sinking  of  the  land  has  admitted  the  sea  to 
the  valleys.     Such  conditions  do  not  favor  dense  settlement. 

145.  Straight  Mountainous  Coasts.  —  The  uplift  of  sea  bot- 
toms is  sometimes  accompanied  by  mountain  folding.  This 
eitlier  raises  narrow  strips  of  coastal  plain,  between  the 
mountains  and  the  sea,  or  else  causes  the  mountains  to  rise 
directly  out  of  the  sea.  Where  the  mountains  rise  from  the 
ocean  in  long  chains  of  folds,  they  produce  a  straight  and 
regular  coast  line. 

Such  a  coast  exists  in  western  America,  from  Oregon  tc 
central  Chile  (Fig.  346).  Along  this  coast  there  are  few 
harbors,  bays,  capes,  and  peninsulas.  In  many  places  the 
mountains  rise  directly  from  the  sea  ;  elsewhere  at  the  inner 
margin  of  a  narrow  coastal  plain  (Fig.  117).  The  sea  bot- 
tom slopes  rapidly,  and,  in  a  short  distance  from  the  coast, 
the  water  is  15,000  or  20,000  feet  deep  (p.  20). 

This  cofist  has  been  recently  elevated,  and,  in  many  places,  is 
still  rising.  Both  in  1822  and  1835  a  part  of  the  coast  of  Chile 
was  suddenly  raised  2  or  3  feet ;  and  beaches  and  sea  shells  on 
the  mountain  slopes  prove  other  recent  uplifts. 

For  several  reasons,  such  coasts  are  not  suited  to  dense  popula- 
tions and  high  development  of  industries.  (1)  There  are  so  few 
harbors  that  a  place,  even  though  on  the  shore,  may  be  a  long  dis- 
tance from  a  shipping  point.  (2)  Between  the  mountains  and  the 
sea  there  is,  at  best,  only  a  narrow  strip  of  fairly  level  laud,  limit- 
ing the  resources.  (3)  The  mountains  act  as  a  barrier  to  inland 
communication,  few,  if  any,  large  streams  breaking  across  them. 
Peru  and  Chile  have  only  recently,  and  at  great  expense,  opened 
railway  communication  across  the  Andes  barrier  (Fig.  184).  The 
scattered  seaports,  therefore,  have  little  country  tributary  to  them. 


Fig.  344.  —  Island  of  Heligoland,  in  the 
North  Sea.  The  outer  line  represents 
it  in  the  year  800,  when  its  circumfer- 
ence was  120  miles  ;  large  shaded  area 
in  1300,  circumference  reduced  by  wave 
erosion  to  45  miles ;  inner  shaded  area 
in  1649,  circumference  only  8  miles. 


SCALE  OF   M1LE3 


BORMAV  i  CO.,  N.Y. 


10 


15 


20 


Fig.  345.  —  Changes  in  the  coast  of  a  part 
of  Asia  Minor,  by  deposits  made  chiefly 
by  the  river  Maeander  (from  which  our 
word  "meander"  is  derived). 


IP 

^^^^H 

F'uj    346. — ^The  straight,  uiountainovis  coast  of 
western  South  America 


Fig.  347  —  An  old  pump  on  the  coast 
of  Ireland,  showing  how  the  waves 
hav»  "vit  awi*?  tibii*  •r^rt.4 


00 

6 


SHORE  LINES,  207 

Summary.  —  Long  chains  of  mountains,  rising  from  the  sea,  form 
straight  coasts,  as  in  luestern  America.  The  scattered  harbors,  the 
narroiv  area  of  level  land,  and  the  mountain  harrier  render  such 
coasts  unsuited  to  dense  settlement  or  high  development  of  industries, 

146.  Irregular  Mountainous  Coasts.  —  Mountain  growth 
makes  irregular  coasts  more  commonly  than  straight  ones. 
Irregular  coasts  result  (1)  when  mountains  rise  as  chains 
of  islands  near  continents,  as  in  the  case  of  the  West  Indies, 
East  Indies,  Philippines,  and  Japanese  Islands ;  (2)  when 
the  ranges  extend  out  from  the  mainland  as  peninsulas,  as 
in  the  case  of  Italy,  Greece,  Alaska,  and  the  Malay  Penin- 
sula ;  and  (3)  when,  between  mountain  ranges,  parts  of  the 
crust  sink,  thus  admitting  the  ocean  and  forming  gulfs  or 
seas,  like  the  Gulf  of  California  and  the  Mediterranean. 

The  Mediterranean  is  a  broad,  deep  depression  (over  14,000 
feet  in  depth)  between  the  mountains  of  Europe  and  Africa.  It 
is  almost  cut  off  from  the  ocean  where  the  Atlas  Mountains  of 
Africa  nearly  meet  the  mountains  of  Spain  at  the  Straits  of 
Gibraltar ;  it  is  almost  connected  with  the  ocean  at  the  low 
Isthmus  of  Suez.  Its  coast  line  is  very  irregular,  because  there  are 
so  many  short  mountain  chains,  extending  in  different  directions. 
These  form  the  peninsulas  of  Tunis,  Italy,  Greece,  and  Asia 
Minor,  besides  many  smaller  projections ;  and  also  chains  of 
islands,  among  which  Cyprus,  Crete,  Sicily,  the  Balearic  Isles, 
and  Corsica  and  Sardinia  are  the  largest.  The  mountain  chain 
of  Italy,  extending  through  Sicily,  and  along  a  submarine  ridge  to 
the  Tunis  peninsula,  almost  cuts  the  Mediterranean  in  two. 

Many  other  large  seas,  such  as  the  Caribbean  Sea,  Gulf  of 
Mexico,  Japan  Sea,  China  Sea,  and  Red  Sea,  are  partly  in- 
closed by  mountain  uplifts.  Still  smaller  seas,  bays,  and 
even  harbors  have  been  made  by  the  uplift  of  mountainous 
islands  and  peninsulas.  Where  there  has  been  a  later  sink- 
ing, as  in  Greece,  the  entrance  of  the  sea  into  the  moun- 
tain valleys  has  made  many  small  bays  and  deep  harbors. 


208  NEW  PHYSICAL   GEOGRAPHY. 

Irregular,  mountainous  coasts  are  better  fitted  for  habitation 
than  straight,  mountainous  coasts.  Communication  by  land  is 
difficult,  and  the  coast  line  is  often  steep  and  rocky  (Fig.  348)  ;  but 
the  many  harbors,  the  great  length  of  the  irregular  coast,  and  the 
quiet  water  of  the  inclosed  seas  and  bays  all  encourage  navigation. 
It  is  largely  because  of  these  conditions  that  navigation  early 
developed  in  the  Mediterranean  (p.  377).  There  are  many  places 
that,  even  to-day,  can  be  reached  only  by  ship ;  and  the  coasts, 
as  in  western  Italy,  are  often  so  mountainous  that  a  railway, 
although  close  by  the  sea,  must  pass  through  a  series  of  tunnels 
near  together.  Wherever  there  is  room  for  towns  or  villages,  as 
on  the  delta  of  a  small  stream,  the  coast  is  well  settled  (Fig.  348) ; 
and,  back  of  the  coast,  the  settlement  is  especially  dense  along  river 
valleys  that  furnish  a  pathway  to  the  sea. 

Summary.  —  Uplift  of  mountainous  islands  and  peninsidas,  and 
sinking  of  the  land  between  mountain  folds,  cause  irregular  coasts. 
Such  coasts,  like  the  Mediterranean,  favor  navigation  because  of  the 
7iumber  of  harbors,  the  length  of  the  coast,  and  the  quiet  water  ;  but 
they  are  frequeyitly  steej),  rocky,  and  sp)arsely  settled.  Communication 
between  places  along  them  must  often  be  by  ship. 

147.  Coasts  of  Drowned  Lands.  —  Sinking  of  the  land  drowns 
a  portion  of  it  and  makes  the  coast  line  irregular  (Fig.  349), 
for  the  valleys  are  then  transformed  to  bays,  harbors,  or  estu- 
aries. Sinking  of  the  land  has  made  San  Francisco  harbor 
(Fig.  350):  _o  has  made  Massachusetts  Bay,  Boston  harbor, 
and  the  other  bays  and  harbors  of  New  England ;  and  it  has 
drowned  the  lower  Hudson  (Fig.  351). 

When  the  hills  of  a  drowned  land  have  been  completely 
submerged,  shoals  and  banks  (p.  197)  are  formed  in  the 
sea.  .  When  the  hills  are  only  partially  submerged,  islands 
are  formed  (Fig.  353),  like  the  British  Isles,  Newfoundland, 
and  the  thousands  of  islands  in  northeastern  (Fig.  354)  and 
northwestern  America.  Where  there  has  not  been  sub- 
mergence enough  to  completely  surround  the  land,  peninsulas 
are  produced,  like  Scandinavia,  Denmark^  Nova  Scotia,  and 
mnumerable  capes  and  promontories  (Fig.  354). 


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Fig.  351.  —  The  drowned  valley  of  the  Hudson,  looking  north  from  West  Point. 


Fio.  352.  — A  Norwegian  fiord. 


tfiG.  354.  —  A  sketch  map  of  a  part  of  the  drowned  coast  of  Maine.     Measure  the 
distance  straight  along  the  coast.    Measure  it  along  the  greater  irregularities. 


Fig.  355.  —  A  small  bay,  or  chasm,  which  the  waves  have  cut  in  the  coast  of 
Cape  Ann,  north  of  Boston.  Here  a  narrow  dike  of  trap  rock  (seen  in  tlie 
middle  of  the  picture)  crosses  the  more  resistant  granite 


SHORE  LINES. 


209 


The  outline  of  a  sunken  coast  depends  upon  the  nature  of  the 
valleys  that  existed  on  the  land  before  it  was  submerged.  Grand 
fiords,  with  wonderful  scenery,  are  formed  where  the  sea  has 
entered  the  deep,  steep-sided,  mountain  valleys  of  Norway  (Figs. 
352,  356)  and  Alaska.  These  fiord  valleys  were  first  cut 
by  streams,  then 
broadened  and  deep- 
ened by  glacial  ero- 
sion. The  Hudson 
is  a  fiord,  and  so  is 
the  Saguenay  in 
Canada. 

Most  fiord  coasts, 
like  that  of  Nor- 
way, are  too  steep 
and  rugged  for 
much  settlement. 
The  villages  are 
usually  on  small 
deltas,  and  very 
often  the  onlv  com- 

munication  between  them  is  by  wate)\     Sush  conditions  account 
for  the  development  of  that  race  of  hardy  sailors,  the  Norsemen. 

The  coast  south  of  New  York  is  strikingly  different  from  the 
rocky  coast  farther  north.  This  difference  is  due  to  the  fact  that 
this  is  a  region  of  soft  rock  and  plains,  crossed  by  broad  valleys 
with  gently  sloping  sides.  The  entrance  of  the  sea  into  these  has 
formed  broad,  shallow  bays  with  gently  rising  margins,  as  in 
Delaware,  Chesapeake,  and  Mobile  bays.  Along  such  coasts 
communication  by  land  is  easy  and  agriculture  thrives. 

There  are  several  reasons  why  moderately  low,  irregular  coasts, 
like  those  of  the  Middle  States,  New  England,  and  England, 
are  favorable  to  settlement  and  development.  (1)  There  is  an 
abundance  of  harbors,  — in  fact,  as  in  Maine  (Fig.  354),  often  far 
more  than  are  needed.  (2)  The  irregularity  makes  a  very  long 
coast  line  for  fishing  and  navigation.  (3)  There  are  protected 
bays  and  sounds  for  fishing  and  navigation.  (4)  Sinking  of  the 
land  opens  up  waterways  to  the  interior.     The  Columbia,  Hud- 


FiQo  356  —A  Norwegian  fiord. 


210  NEW  PHYSICAL   GEOGRAPHY, 

sou,  and  Thames  are  navigable  to  ocean  ships  solely  because 
recent  sinking  has  admitted  the  sea.  Portland,  New  York,  and 
London  could  not  otherwise  be  important  seaports. 

The  formation  of  islands  cuts  off  connection  with  the  mainland 
and  produces  very  important  effects  on  the  inhabitants.  Thus 
Newfoundland  is  so  isolated  that  its  interests  are  different  from 
those  of  the  Canadian  provinces,  and  it  has  declined  to  join  the 
Canadian  Confederation.  The  sinking  of  the  land,  which  sepa- 
rated  Great  Britain  from  Europe  at  the  Strait  of  Dover,  has  pro- 
tected the  British  from  inroads  of  invaders  by  land,  and  has 
forced  the  development  of  navigation  and  a  navy  (p.  389). 

Summary.  —  Sinking  of  the  land  forms  bays,  harbors,  and  estua- 
ries in  valleys,  ayid  makes  shoals,  banks,  islands,  aiid  j^^'^^insidas 
of  hills,  thus  making  the  coast  irregular.  The  submergence  of 
mountainous  regions  forms  fiords,  and  a  rugged  coast  suited  to  navi- 
gation, but  not  to  dense  settlement.  Regions  of  soft  rock,  when 
drowned,  have  broad,  shalloiv  bays  with  gently  sloping  sides,  adapted 
to  agriculture.  Moderately  low,  irregular  coasts  favor  development 
because  of  the  harbors,  the  favorable  conditions  for  fishing  and 
namgatioyi,  and  the  opening  of  ivaterivays  to  the  iyiterior.  The  forma- 
tion of  islands  isolates  people  and  greatly  influences  their  history. 

148.  Wave  and  Tide  Work.  —  Waves  are  constantly  batter- 
ing at  the  coast  line,  cutting  cliffs  where  possible  and  moving 
the  fragments  about  (p.  186).  Some  of  the  sediment  is 
dragged  offshore  by  the  undertow  and  tidal  currents  ;  some  is 
drifted  along  the  coast  by  the  waves  and  the  tidal  and  wind- 
formed  currents.  On  rocky  coasts  this  shore  drift  lodges 
between  headlands,  forming  beaches  (Fig.  364)  ;  on  low, 
sandy  coasts  it  is  built  into  long  sand  bars  (Fig.  372). 

Waves  and  currents  are  accomplishing  two  ends  by  this 
work :  (1)  cutting  back  the  land,  (2)  straightening  the 
coast.  An  irregular  coast  will  not  long  be  tolerated  by 
waves  and  currents;  and,  Ave  re  it  not  for  the  fact  that  there 
are  so  many  movements  of  the  crust,  the  coast  lines  of  the 
world  would  all  be  straight.     When,  therefore,  we  find  an 


Fig    357- A.  wave-cut  ciiasui  m  lur  rot-k^  on  the  Maine  coast. 


Fig.  358.  —  A  wave-cut  cliff  in  tiie  clay  on  the  shore  of  Lake  Ontario.  This  cliff 
is  beins^  cut  backward  at  the  rate  of  about  two  feet  a  year ;  and,  by  this  cut- 
ting, trees  are  undermined  and  caused  to  slide  down  the  cliff  face. 


Fig.  359.  —  A  sea  cave  which  the  waves  have  cut  on  the  Maine  coast.     The  dark 
area  in  front  is  the  seaweed  mat  which  the  high  tide  covers. 


Fig.  360.  —  A  rock  cliff  on  the  Maine  coast,  showing  how  the  waves  sometimes 
undercut,  causing  the  hard  rotK  to  overhang.  The  dark  area  in  the  fore- 
ground is  the  seaweed  mat,  covered  at  liigh  tide. 


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Fig.  361. — A  cliff  in  glacial  deposit  on  the  Massa-dhusetts  coast.  The  waves 
have  not  heen  able  to  remove  the  large  bowlders  that  were  in  the  deposit, 
and  they,  therefore,  remain  as  an  offshore  platform,  showing  that  the  land 
once  extended  out  so  far. 


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SHORE  LINES,  211 

irregular  coast,  we  may  be  certain  that  the  shore  has  not  stood 
long  enough  at  that  level  for  the  waves  and  currents  to 
straighten  it.  This  work  of  straightening  coast  lines  is  done 
in  two  ways —  (1)  by  cutting  back  the  headlands  and  (2)  by 
closing  up  and  filling  the  indentations. 

Summary.  —  Wcwes  and  currents  are  attacking  the  headlands  and 
moving  the  fragmerits  either  offshore  or  cdong  the  coast,  in  the  latter 
case  building  beaches  and  bars.  The  result  of  this  work  is  to 
straighteyi  the  coast. 

149.  Sea  Cliffs.  —  Where  wave  work  is  vigorous,  as  on 
headlands  and  on  exposed  island  coasts,  the  waves  are  saw- 
ing into  the  land  (Figs.  344,  347).  The  zone  of  most  active 
wave  work  is  almost  exactly  at  the  sea  level,  though  the 
spray  may  dash  to  a  height  of  50  or  100  feet.  The  advanc- 
ing breakers  hurl  against  the  cliffs  tons  of  water,  bearing  sand, 
pebbles,  and  even  bowlders.  They  act  like  battering  rams, 
undercutting  the  cliffs  along  the  surf  line  (Fig.  360),  and 
thereby  undermining  the  rock  so  that  it  falls  and  keeps  the 
cliff  face  precipitous. 

If  made  of  hard  rock,  sea  cliffs  are  very  steep  (Fig.  362), 
though  weathering,  aided  by  the  salt  spray,  usually  prevents 
them  from  becoming  vertical.  If  made  of  clay  or  sand,  the 
cliffs  are  steeply  inclined  and  constantly  sliding  down  (Figs. 
358,  361,  367).  On  exposed  coasts,  sea  cliffs  may  rise  several 
hundred  feet;  but  generally  they  are  much  lower. 

Cliffs  in  which  the  rocks  have  uniform  texture  may  be  straight 
and  regular;  but  if  the  strata  vary,  the  waves  discover  the  differ- 
ences and  make  the  shore  irregular.  Then  chasms  (Figs.  355,  357) 
and  sea  caves  (Fig.  359)  are  cut  in  the  cliffs  along  the  weaker 
strata.  These  irregularities  cannot  be  cut  very  far  back  into  the 
land,  nor  to  a  very  great  breadth,  because  the  force  of  the  waves 
is  soon  worn  out  on  the  sides  and  bottom.  For  this  reason,  waves 
cannot  carve  out  large  bays. 

Sea  cliffs  may  be  cut  back  for  hundreds  of  feet,  leaving  a  plat- 
form of  rock  (Figs.  361,  362)  which  the  waves  continue  to  plane 


21^  NE}V  PHYSICAL   GEOGTtAPHY, 

down  until  they  no  longer  break  upon  it.  In  the  open  ocean  entire 
islands  have  been  cut  away  by  waves  (Fig.  234);  leaving  only 
shoals  or  reefs.  As  the  cliffs  wear  back,  farms  and  houses  are 
undermined  and  caused  to  tumble  into  the  sea. 

Such  headlands,  with  their  offshore  platforms,  are  dangerous  to 
navigation ;  and  a  vessel  wrecked  upon  the  wave-beaten  reefs  is 
doomed.  There  is  little  hope  that  the  shipwrecked  sailors  can 
escape,  for  there  is  no  landing  place  on  the  cliffs,  and  the  waves 
are  ever  breaking  on  the  reefs  near  their  base.  It  is  partly  for 
this  reason,  and  partly  because  of  their  height,  that  headland 
cliffs  are  commonly  selected  as  the  sites  of  lighthouses  (Fig.  362). 

Summary.  —  The  sawing  of  the  waves  into  the  land  cuts  sea  cliffs, 
leaving  offshore  platforms  as  the  cliffs  are  pushed  hack.  Weather- 
ing 2^^'events  most  cliffs  from  being  vertical,  hut  all  are  steep,  even 
those  in  sand  or  clay.  Where  there  are  differences  in  the  rocks,  chasms, 
sea  caves,  and  other  small  irregularities  are  produced.  Headland 
cliffs  and  offshore  platforms  are  dangerous  to  navigation. 

150.  Beaches,  Hooks,  Bars,  etc.  —  Bowlder  (Fig.  363)  and 
pebble  beaches  (Fig.  364)  are  built  of  the  larger  rock  frag- 
ments, wrested  from  the  cliffs  and  driven  along  the  coast, 
till  they  lodge  in  bays.  Smaller  fragments  make  sand 
beaches  (Fig.  365)  ;  and  the  still  finer  clay  settles  in  the 
protected  bays,  harbors,  and  estuaries,  forming  mud  banks 
and  flats.  Some  fine-grained  sands  form  quicksands.  In  these 
are  numerous  particles  of  mica,  which  permit  the  sand  grains 
to  slip  over  one  another  when  wet,  so  that  an  object  sinks 
into  the  sand. 

In  little  pockets  between  headlands  there  are  often  small 
^'  pocket "  beaches,  sometimes  called  "  half  moon  "  beaches,  be- 
cause of  their  crescentic  shape  (Figs.  363,  366).  Behind  them 
small  ponds  are  often  shut  in.  On  exposed  coasts  these  beaches 
are  of  bowlders  or  pebbles  ;  in  more  protected  places,  of  sand. 
The  beaches  serve  as  mills,  in  which  rock  fragments  are  ground 
so  fine  that  they  can  be  borne  off  by  the  currents  and  undertow. 
The  rounded  form  of  beach  pebbles  shows  how  they  are  rolled 
about. 


Fia.  363.  —  A  bowlder  pocket-beach  on  the  exposed  coast  of  Cape  Ann,  Mass. 


-■-''^u.r'v 


Fig.  364.  —  a  pebble  beach  on  the  coast  of  Cape  Ann,  Mass.    Notice  how  round 
the  pebbles  are.    High  waves  reach  clear  to  the  top  of  the  beach. 


Fig.  365.  —  A  sand  beach,  with  sand  dunes  piled  upon  the  landward  side  by  the 

action  of  the  winds. 


tf^Q.  366.  —  A  cresceut  beach  in  a  small  bay  harbor  on  Santa  Catalina  Island, 
Cal.  One  portion  of  the  cliffs  that  supply  this  beach  is  seen  on  the  right,  in 
the  distance.  There  the  waves  have  not  quite  consumed  the  land,  but  have 
left  a  part  standing  as  an  island. 


Fig.  367.  —Highland  Licrht  cliff  on  the  bacK  shore  of  Cane  Cod.  ^Fig.  375).  This 
cliff  of  loose  sand  is  wearina:  back  so,  fast  that  little  vegetation  is  able  to 
find  root  on  its  slippmg  face.  It  is  suppJyni^  sand  for  the  waves  and  t\..t- 
.~^nt«  to  drift:  along  the  coast  and  build  -nto  sand  bars  and  shoala 


Fig.  368.  — A  view  of  the  Sandy  Hook  bar  from  the  Navesink  Highlands  in  New- 
Jersey. 


Fig.  369.  —  A  bar  joining  a  small  island  to  the  land  on  the  coast  of  Sicily. 


Fig.  370.  —  A  bar  at  North  Fairhaven,  N.Y.,  on  the  shore  of  Lake  Ontario, 
partly  shutting  in  a  broad  bay.  The  opening  is  maintained  by  the  out- 
flow of  water  from  the  land  streams.  The  pebbles  of  which  this  bar  is 
Ciade  are  supplied  from  a  number  of  cliffs,  of  which  Fig.  358  is  one. 


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SHORE  LINES. 


513 


BOflMAY   Sc  CO.,   N.Yi 


Fig.  373.  —  A  portion  of  the  south  shore  of  Marthas 
Vineyard,  showing  how  the  growth  of  sand  bars 
may  straigliten  an  irregular  coast  by  shutting  in 
the  bays  and  changing  them  to  ponds. 


Some  of  the  rock  fragments  that  are  moved  along  the  coast 
are  dropped  at  the  entrance  to  bays,  building  bars  across 
them  (Fig.  373).  If  there  is  much  drainage  from  the  land, 
an  opening  through  the  bar  will  be  maintained  (Fig.  370); 
but  if  not,  a  bar  may  completely  seal  a  bay  (Fig.  373).  A 
fresh- water  pond 
then  gathers  be- 
hind the  bar,slowly 
draining  through 
it  by  seepage. 

On  manv  coasts, 
where  there  is  an 
abundant  supply  of 
sand,  long  bars  are 
built.  For  ex- 
ample, the  waves 
are  vigorously 
wearing  back  the 
high  cliffs  (Fig.  367)  at  Highland  Light,  Cape  Cod,  and 
building  bars  out  of  the  sand  (Fig.  375).  In  the  same  way 
Sandy  Hook  (Fig.  368)  has  been  built  of  debris  worn  from 
the  cliffs  of  the  New  Jersey  shore. 

Such  bars  may  be  straight,  or  they  may  be  curved  at  one  end, 
forming  liooks  (Fig.  374),  like  Sandy  Hook  (Fig.  368)  and  the 
curved  end  of  Cape  Cod  (Fig.  375).  In  some  places,  often  at 
bends  in  the  shore,  waves  and  currents  from  opposite  directions 
drive  pebbles  or  sand  out  into  the  water,  building  small  points,  or 
spits.  Bars  sometimes  form  an  angle  projecting  seaward,  making 
a  Gusj),  like  Capes  Hatteras,  Fear,  Lookout,  and  Canaveral.  Other 
bars  are  often  built  in  the  lee  of  islands  (Fig.  369). 

Summary.  —  Rock  fragments,  drifted  along  the  coast,  build  beaches 
in  pockets,  bars  across  bays,  long  bars  where  large  quantities  of  sand 
are  supplied;  cdso  hooks,  spits,  and  cusps.  Tlie  matericd  varies 
from  botvlders  to  sand,  much  of  the  Jimc  clay  going  into  the  bays. 
Tlie  beaches  are  mills  in  which  rock  fragments  are  ground  up. 


214 


NEW  PHYSICAL   GEOGRAPHY. 


Fig.  374.  —  A  hook  in  one  of  the  Bras  d'Or  Lakes  (realiy  au  arm  of  the  sea)  in  Cape 
Breton  Island,  Nova  Scotia.  It  is  made  of  pebbles  driven  out  into  the  water 
by  the  waves. 

151.  Offshore  Bars.  —  From  New  Jersey  to  the  Rio  Grande 
most  of  the  coast  is  faced  by  bars  at  some  distance  from  the 
mainland,  from  which  they  are  separated  by  shallow  lagoons 
(Fig.  372).  One  of  the  longest  of  these  bars  extends  along 
the  Texas  coast  from  the  mouth  of  the  Rio  Grande  (Fig.  371). 
River  water  enters  the  lagoons,  some  of  it  seeping  through  the 
bar,  the  remainder  escaping  through  gaps  that  the  outflowing 
and  incoming  tide  are  able  to  keep  open.  The  movement  of 
sand  along  the  shore  constantly  threatens  to  close  these  chan- 
nels; and  for  this  reason,  where  the  channels  are  used  as 
harbor  entrances,  as  at  Galveston,  it  is  necessary  to  build 
jetties  to  keep  the  entrance  deep  enough  for  large  ships. 


Such  offshore  bars,  or  barrier  beaches,  are  thrown  up  where 
waves  advance  over  a  shallow  bottom  of  unconsolidated  sedi- 


SHORE  LINES.  215 

ment.  The  shallowness  interferes  with  the  onward  movement 
of  the  waves,  and  where  they  commence  to  break,  the  sand  is 
pushed  up  into  a  ridge  or  bar.  The  wind  builds  the  bars  still 
higher,  raising  sand  dunes  (Figs.  376,  377),  sometimes  100  feet 
high.  The  waves  gradually  consume  the  sand  bars,  eating  them 
away  on  the  seaward  side  and  pushing  them  back  toward  the  land. 
Beaches  and  bars  are  often  useful  as  places  for  landing  boats 
(Figs.  348,  366) ;  and  for  bathing  they  are  resorted  to  by  hundreds 
of  people.  Offshore  bars  are,  in  addition,  habitable,  though  usually 
so  sterile  that  they  are  inhabited  only  by  fishermen,  lighthouse 
keepers,  and  pleasure  seekers.  Yet  some  bars,  like  the  Sea 
Islands  off  the  Georgia  coast  (Fig.  376),  where  the  long-fibered 
Sea  Island  cotton  is  raised,  are  excellent  farm  land.  Here  and 
there,  too,  because  of  the  absence  of  other  kinds  of  harbors  on 
such  coasts,  towns  and  cities,  like  Galveston,  are  built  on  the 
sand  bars.  The  destruction  at  Galveston  in  1900  (Fig.  429) 
proves  that  cities  in  such  situations  are  in  danger  of  inundation. 

The  sand  that  is  drifted  about  in  the  building  of  sand  bars 
often  makes  dangerous  shoals.  The  shifting  sands  south  of  Cape 
Cod,  and  those  near  Sandy  Hook,  are  obstacles  to  safe  naviga- 
tion ;  and,  on  the  shoals  at  the  end  of  Cape  Hatteras,  many 
ships  have  been  wrecked. 

Summary.  —  Where  the  waves  break  on  shallow  sea  bottoms  the 
sand  is  pushed  up  into  ridges,  or  offshore  bars,  ivhich  are  raised  still 
higher  by  the  wind.  Such  bars,  inclosing  lagoons,  are  found  along 
much  of  the  coast  from  New  Jersey  to  the  Rio  Grande. 

152.  Sand  Dunes  of  the  Seacoast.  —  On  beaches,  as  in  des- 
erts (p.  88),  there  is  dry  sand,  which  the  wind  drifts  about, 
often  piling  it  up  in  low  hills  and  ridges,  or  sand  dunes.,  along 
the  upper  edge  of  the  beach  (Fig.  365).  Sand  dunes  are  ex- 
ceedingly irregular  (Fig,  377),  and  their  form  is  ever  chang- 
ing. Between  the  dune  hills  are  basins,  in  which,  however, 
there  is  rarely  any  water,  because  the  bottom  is  so  porous. 

The  movement  of  sand  inland,  doing  much  damage,  is  some- 
times made  possible  by  the  removal  of  a  forest,  which  gives 


216  NEW  PHYSICAL   GEOGRAPHY- 

full  sweep  to  the  wind.  The  removal  of  a  forest  back  of  Coffin'* 
Beach  on  Cape  Ann,  Mass.,  over  a  century  ago,  permitted  the 
sand  to  move  inland  and  destroy  a  farm.  Dunes  in  France  have 
moved  inland  two  or  three  miles,  destroying  farms  and  villages 
to  such  an  extent  that  the  French  government  has  taken  up  the 
problem  of  how  to  stop  their  further  advance.  This  is  being 
done  by  planting  trees  behind  the  dunes,  and  setting  out  such 
plants  as  will  grow  in  the  sterile,  sandy  soil. 

A  sand-dune  region  is  difficult  to  cross  on  account  of  the  loose 
sand,  and  of  little  use  to  man  because  the  soil  is  so  sterile.  But 
in  the  Netherlands  the  sand  dunes  protect  the  low  plains  from 
submergence.  The  waves  are  consuming  this  coast,  having  cut 
it  back  two  miles  in  historic  times.  As  the  waves  consume  the 
beach  the  row  of  dunes  behind  the  beach  is  slowly  pushed 
inland. 

Summary.  —  Along  many  coasts  irregular  sand  hills,  or  dunes, 
are  built  up  by  the  wind,  and  their  advance  inland  has  in  some  cases 
caused  the  destruction  of  much  property.  In  the  Netherlands  the 
sand  dunes  act  as  a  barrier,  protecting  the  low  plains  from  the  ivaves. 

153.  Salt  Marshes. — Sediment  deposited  in  estuaries,  in 
lagoons  behind  sand  bars  (Fig.  372),  and  in  other  protected 
arms  of  the  sea,  is  slowly  filling  them.  Salt-water  plants  that 
flourish  in  these  places,  such  as  the  eel  grass  and  salt-marsh 
grasses,  aid  in  the  filling.  Their  aid  consists  partly  in  add- 
ing their  own  remains,  partly  in  checking  the  currents,  thus 
causing  them  to  drop  some  of  the  sediment  they  carry. 

In  time,  the  deposit  of  sediment  and  plant  remains  reaches 
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of  the  salt-marsh  plants.  By  this  process,  nature  is  engaged 
in  reclaiming  much  land  from  the  sea. 

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SHORE  LINES.  217 

^ailt  to  exclude  the  sea,  and  the  land  drained,  salt  marshes  make 
excellent  farm  land.  jMuch  of  the  fertile  lowland  of  England,  a 
large  part  of  the  Netherlands,  and  the  beautiful  Evangeline  coun- 
try of  Xova  Scotia  are  diked,  marsh  land.  In  the  United  States 
little  has  been  done  to  reclaim  salt  marsh,  because  we  have  had 
enough  land  without  it.  But  the  time  cannot  be  far  distant  when 
the  extensive  salt  marshes  near  New  York  and  Boston  will  repay 
diking.  Boston  is  partly  built  on  salt  marsh  that  has  been  changed 
to  dry  land  by  filling  with  earth  removed  from  neighboring  hills. 

Summary.  —  //i  protected  hays  and  lagoons,  sediment  and  the 
remains  of  salt-water  plants  build  up  salt-marsh  plains.  In  places 
these  have  been  reclaimed  by  dikes  or  by  filling. 

154.  Mangrove  Swamps.' — ^ Mangrove  trees  grow  in  protected 
spots  on  the  coasts  of  warm  countries,  such  as  the  Philippines, 
Bermuda  Islands,  and  southern  Florida.  The  mangrove  tree  (Fig. 
379)  is  firmly  anchored  by  roots  that  descend  from  the  branches, 
forming  an  almost  impenetrable  jungle,  or  mangrove  swamp. 

Summary.  —  In  warm  countries  the  salt  rtiarsh  is  replaced  by  the 
almost  impenetrable  jungle  of  the  mangrove  swamp. 

155.  Coral  Reefs.  —  On  some  warm  coasts  animal  life  is  so 
abundant  that  tlie  shore  is  made  entirely  of  animal  remains. 
Of  these  animals,  corals  are  the  most  important.  Reef- 
building  corals  thrive  only  in  depths  less  than  150  feet,  where 
there  is  little  sediment,  little  fresh  water  from  the  land, 
currents  bringing  abundant  food,  and  a  temperature  never 
below  70°. 

Coral  is  made  by  lowly  animals,  of  which  there  are  many 
species,  varying  in  size  from  almost  microscopic  to  individuals 
several  inches  in  diameter.  Some  species  live  singly,  but  most 
unite  in  colonies,  together  forming  a  limy  framework  (as  animals 
form  their  bones),  which  we  call  coral.  Some  corals  are  massive, 
Dowlder-like  domes,  others,  delicately  branching,  treelike  forms. 
The  individuals,  or  2^oly2)s,  which  form  the  coral,  dwell  in 
little  cavities  that  dot  its  surface.     The  coral   mass  is  alive  on 


218  NEW  PHYSICAL   GEOGRAPHY. 

the  outside,  dead  on  the  inside,  and  the  polyps  build  their  coral 
homes  on  foundations  laid  by  former  generations. 

The  polyps  can  either  withdraw  into  the  cavities  or  extend 
their  branching  arms  into  the  water  in  search  of  food.  To  one 
looking  down  upon  a  coral  reef,  through  a  box  with  a  glass  bottom, 
the  sea  floor  seems  like  a  garden,  with  flowers  of  all  colors  and 
many  forms  ;  and  among  the  corals  are  myriads  of  other  animals, 
some  fixed  in  place,  some  moving  freely  about.  The  abundance 
and  variety  of  life  in  such  a  place  is  marvelous. 

Coral  growth  is  most  rapid  on  the  outer  side  of  a  reef, 
where  food  is  most  abundant.  This  causes  reefs  to  grow 
seaward,  and  their  outward  growth  is  increased  by  the  action 
of  the  waves,  which  break  off  coral  fragments  and  drag  them 
out  to  sea.  A  reef  may  start  close  to  shore,  as  a  fringing 
reef  and  advance  so  far  that  it  becomes  a  harrier  reef. 
Another  way  in  which  a  fringing  reef  may  be  changed  to  a 
barrier  reef  is  by  a  slow  sinking  of  the  land.  If  the  coral 
grows  upward  as'  fast  as  the  land  sinks,  it  will  form  '^  reef 
farther  and  farther  from  the  sinking  land. 

There  are  coral  reefs  on  many  coasts,  the  longest  in  the 
world  being  the  Great  Barrier  Reef  (Fig.  380),  which  for 
over  1000  miles  skirts  the  northeastern  coast  of  Australia  at 
a  distance  of  20  to  50  miles.  Behind  it  i^  a  navigable  lagoon 
of  quiet,  protected  water,  in  which,  however,  a  good  pilot 
is  necessary,  because  of  the  many  coral  shoals. 

Uplift  of  the  coast  adds  coral  reefs  to  the  land,  in  the  form  of 
terraces,  like  those  in  Cuba  and  other  islands.  Even  in  the  inte- 
rior of  continents,  fossil  reefs  are  found  in  some  of  the  limestone 
strata  that  were  deposited  in  ancient  oceans. 

Waves  and  winds  often  heap  the  coral  fragments  above  sea 
level,  forming  land,  as  in  the  Bermuda  Islands.  The  Bermudas, 
whose  base  beneath  the  sea  is  a  volcanic  cone,  are  surroimded  by 
a  fringe  of  coral  reefs.  Fragments,  broken  from  the  reefs  by  the 
waves,  are  ground  on  the  beaches  to  coral  and  shell  sand,  then 
drifted  inland   by  the  winds,  forminc  sand   dunes.      These  are 


SHORE  LINES.  219 

quickly  cemented  into  a  soft  rock  by  the  deposit  of  carbonate  of 
lime  around  the  grains.  The  Bahamas,  and  many  other  coral 
islands,  are  made  in  the  same  manner.  The  soil  of  such  dunes  is 
far  better  than  the  soil  of  ordinary  sand  dunes. 

Summary.  —  In  tvarm,  clear  water,  where  there  is  an  abundance 
of  food  for  fixed  animals,  corals  thrive,  building  limy  skeletons,  out 
of  ivhich  reefs  are  made.  Fringing  reefs  are  made  along  the  coast, 
and  these  may  change  to  barrier  reefs  either  by  outward  growth  or  by 
sinking  of  the  land.  T7ie  ivind  often  forms  dunes  of  the  coral  sand 
drifted  from  the  beaches,  thus  making  land  m  the  sea. 

156.  Atolls.  —  Ring-shaped  islands  in  the  open  ocean,  made 
of  coral  fragments,  are  called  atolls  (Fig.  382).  A  channel 
into  the  interior  lagoon  is  kept  open  by  the  incoming  and 
outgoing  tides.  Atolls  are  especially  common  in  the  South 
Pacific,  and  are  in  some  cases  several  miles  in  diameter, 
though  rarely  rising  more  than  12  to  15  feet  above  sea  level. 
They  are  so  low  that  during  hurricanes  they  are  sometimes 
inundated  by  the  sea.  Like  the  Bermudas,  the  part  above 
water  is  made  of  coral  and  shell  fragments  that  the  waves  have 
thrown  on  the  beach  and  the  wind  drifted  into  low  hills. 

Few  animals  have  reached  these  remote  islands  ;  but  there 
are  numerous  plants,  including  the  cocoanut  palm.  Many 
atolls  are  inhabited  by  man. 

Atolls  are  built  on  the  peaks  of  extinct  volcanoes  that  -rise 
from  the  sea  bottom.  Sometimes  they  seem  to  have  been  built 
on  !i  ibmerged  peaks,  the  ring  shape  being  due  to  the  faster  growth 
on  the  outside  of  the  reef,  while  within  the  lagoon  much  of  the 
lime  of  the  coral  is  removed  by  solution.  In  other  cases  the 
atolls  appear  to  be  due  to  a  slow  subsidence  of  volcanic  cones 
(Fig.  385).  According  to  this  explanation  there  was  first  a  vol- 
canic island  surrounded  by  a  fringing  reef  (Fig.  381);  by  slow 
sinking  this  changed  to  a  barrier  reef  ;  finally,  when  the  cone  had 
entirely  disappeared,  there  was  a  ring-shaped  atoll  where  the 
cone  formerly  rose.  The  sinking  of  the  cone  could  have  been 
EO  faster  than  the  upward  c:rowth  of  the  reef. 


220  NEW  PHYSICAL   GEOGRAPHY. 

Summary.  — Low,  ring-shaped  coral  islands  in  the  open  ocean  are 
ccdled  atolls.  They  are  built  on  volcanic  cones.  In  some  cases  at 
least,  they  are  caused  by  a  subsideyice  of  the  cone  at  about  the  same 
rate  as  the  upward  growth  of  a  fringing  reef 

157.  Lake  Shores.  —  Most  that  has  been  said  about  sea> 
coasts  applies  quite  fully  to  lakes ;  and  illustrations  of  most 
shore-line  phenomena  are  found  along  lake  shores.  There  are 
headlands,  Avave-cut  cliffs,  beaches,  bars,  sand  dunes,  islands, 
promontories,  and  harbors.  There  are  also  elevated  and 
drowned  coasts.  In  fact,  from  tlie  form  alone  it  is  quite 
impossible  to  distinguish  lake  from  ocean  shores.  Figures 
358  and  370  are  from  lake  shores. 

It  is  true  that  tides  are  absent  in  all  but  the  largest  lakes, 
and  even  there  are  almost  unnoticeable  ;  and,  because  the 
waves  are  less  violent,  the  cliffs  are  usually  smaller,  resem- 
bling those  of  bays  rather  than  the  open  ocean ;  but  in  great 
lakes  there  are  some  high  cliffs. 

The  effects  of  life  are,  however,  quite  unlike  in  the  two  cases. 
Although  swamps  are  formed  in  the  lagoons  and  bays  of  lakes, 
the  plants  are  very  different  from  those  of  the  salt  marsh ;  and 
the  absence  of  tide  makes  the  difference  between  lake  and  sea- 
shore swamps  even  more  marked.  In  lakes  there  are  no  corals, 
and,  consequently,  no  coral  reefs. 

Summary.  —  Lah:e  and  sea-coasts  are  so  alike  that,  from  the  form 
alone,  they  could  not  be  distinguished.  The  chief  differences  are  the 
smaller  cliffs,  the  absence  of  tides,  and  the  effects  of  life. 

158.  Abandoned  Shore  Lines.  —  In  many  places  where  lakes  have 
disappeared,  clitfs  and  beaches  are  now  found  on  the  land.  For 
example,  very  perfect  beaches,  bars,  spits,  and  cliffs  are  found 
near  Great  Salt  Lake,  marking  the  shore  line  of  ancient  Lake 
Bonneville  (Fig.  301).  Similar  shore  lines  mark  the  level  reached 
by  the  glacial  lakes  in  the  valleys  of  the  Ked  River  of  the  North 
(Fig.  130)  and  the  Great  Lakes  (p.  150).  Such  beaches  are  seen  at 
or  near  Duluth,  Chicago,  Cleveland,  Rochester,  Syracuse,  and 
many  other  points.     They  are  so  much  like  ocean  shore  line? 


Fig.  383.  —  A  wave-cut  cliff  on  the  French  coast.  In  cutting  back  the  land, 
the  waves  have  left  a  "  stack  "  island.  Another  will  be  formed  when  the 
roof  of  the  wave-cut  cave  falls. 


^G.  384.  —  Elevated  wave-cmt  cliff  on  the  west  coast  of  southern  Scotland. 
Just  beyond  this  ciiff  is  a  sea  cave  with  fields  extending  up  to  it. 


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Fig.  388.  —  The  drowned  coast  of  a  part  of  southern  New  England.  Notice  the 
small  hays  partly  or  completely  shut  in  by  bar*.  (A  part  of  the  United 
fctates  Geological  Survey   ^^ew  London,  ^onn.,  Sheet.) 


^rlMAY    &    CO.,    N.V. 


Contour  Interval  20  ftet. 
J}atum  In  meart  S«a  LtttL 


Fia.  389. — The  drovvned  coast  of   a   part  of  Maine.      (United  States  Geological 

Survey^  Boothbay,  Maine.  Sheet) 


SHORE  LINES,  221 

that  for  a  while  they  were  supposed  to  have  been  caused  by  a 
sinking  of  the  land,  admitting  the  sea  into  these  valleys. 

Elevated  sea  beaches  are  found  from  southern  iSTew  England  to 
Baffin  Land.  Near  Boston  these  beaches  are  from  40  to  60  feet 
above  sea  level ;  in  Labrador  several  hundred  feet.  There 
are  also  elevated  beaches  in  Norway,  Scotland,  and  other  parts 
of  northwestern  Europe.  Here  the  country  back  of  the  elevated 
shore  lines  is  irregular,  rocky,  and  not  well  suited  to  farming ;  but 
between  the  elevated  beaches  and  the  present  shore  is  a  narrow 
plain  which  is  good  farm  land  and  well  settled.  It  is  an  elevated 
sea  bottom,  from  which  the  waves  have  partly  removed  the  islands 
and  promontories,  and  over  which  sediment  has  been  strewn 
(Fig.  386).  Proof  of  former  wave  work  at  these  higher  levels 
is  furnished  by  elevated  beaches,  marine  fossils,  islands  partly 
cut  away,  and  cliffs  (Fig.  384)  with  sea  caves  and  chasms. 

Summary.  —  Shore  lines,  closely  resembling  marine  shore  lines, 
Tuiark  the  sites  of  extinct  lakes;  and  elevated  sea  beaches  are  found 
in  northeastern  America  and  northwestern  Europe. 

159.  Life  History  of  a  Coast  Line.  —  Elevations  and  depres- 
sions of  tlie  land  are  so  frequent  that,  before  the  waves  have 
carried  their  work  very  far,  some  change  in  level  brings  new 
regions  within  their  reach.  If  a  coast  were  allowed  to  pass 
through  its  life  history  uninterrupted,  the  changes  would  de- 
pend on  the  nature  of  the  rock,  the  form  of  the  coast,  and 
the  force  and  direction  of  waves  and  currents. 

We  will  start  with  a  rocky,  irregular,  exposed  coast,  like 
that  of  New  England,  —  a  typical  young  coast  line  (Fig.  386). 
Slowly  the  headlands  are  cut  back  (Figs.  362,  383),  some  of 
the  materials  being  moved  offshore,  some  driven  along  the 
coast.  Of  the  materials  driven  alongshore,  bars  are  made, 
tying  islands  to  the  mainland  (Fig.  369)  and  closing  the  bays 
(Figs.  370,  373).  Sediment  slowly  fills  the  bays,  transform- 
ing them  to  salt  marshes  (Fig.  378),  then  to  dry-land  plains. 
This  straightened  coast  is  a  mature  coast  line.  As  the  waves 
continue  to  cut  back  the  headlands,  the  beaches  and  bars  are 
also  pushed  back,  and  thus  the  entire  coast  line  retreats. 


222  NEW  PHYSICAL   GEOGBAPHY. 

If  the  rock  is  weak,  less  time  is  required  for  this  life  history  •, 
and  if  at  the  beginning  the  coast  is  not  very  irregular,  less  time 
is  required  to  straighten  it.  On  coasts  of  loose  sand  and  clay, 
with  gently  sloping  bottom,  cliffs  are  first  cut,  then  offshore  bars 
are  thrown  up  (Figs.  371,  372,  387).  As  in  the  case  of  other 
straightened  coasts,  the  waves  then  gradually  push  the  barrier 
beaches  back  toward  the  land.  Coral  coasts  have  a  different  life 
history,  for  they  depend  on  the  growth  of  animals. 

Summary.  —  Young  coasts  are  irregular  ;  as  they  advance  toward 
maturity  lieadlayids  are  cut  hack,  hay  mouths  are  closed,  and  irregu- 
larities are  filled  ;  then  both  headlands  and  beaches  are  slowly  moved 
backward  as  the  land  is  consumed,  TJiis  life  history  requires  a  longer 
time  in  hard  than  in  soft  rock.  On  gently  sloping  coasts  of  soft  rock, 
one  of  the  earliest  stages  is  the  building  of  offshore  bars, 

160.  Islands  and  Promontories.  —  Perhaps  the  greatest 
number  of  islands  and  promontories  are  due  to  sinking  of  the 
land  (Figs.  349,  352-354,  388,  389),  as  illustrated  by  those 
of  northeastern  and  northwestern  America,  northwestern 
Europe,  southern  South  America,  and  the  Grecian  coast. 

Other  islands  and  promontories  are  built  by  mountain 
growth  (pp.  98,  207).  Alaska,  Lower  California,  the  West 
Indies,  the  large  peninsulas  and  islands  of  the  Mediter- 
ranean, Madagascar,  New  Zealand,  the  East  Indies,  the  Malay 
Peninsula,  the  Philippines,  the  Japanese  islands,  Korea,  and 
many  chains  of  oceanic  islands  are  of  this  origin.  Many 
islands  in  the  open  ocean  are  volcanoes  (pp.  124, 175)  ;  for  ex- 
ample, the  Azores,  Canaries,  Madeiras,  and  Hawaiian  Islands. 

Atolls  and  many  coral  reefs  are  islands  built  by  animal  life, 
aided  by  waves  and  wind  (p.  218).  These  are  illustrated  by  the 
Bahamas,  Bermudas,  and  the  islands  off  southern  Florida,  includ- 
ing Key  West.  Some  coral  reefs  are  attached  to  the  land,  forming 
promontories.  The  formation  of  barrier  beaches  (p.  214)  is  another 
cause  for  islands  and  promontories  (Figs.  368,  375),  as  illustrated 
along  the  coast  of  the  United  States.  Deltas  are  often  prom- 
ontories; and  along  their  shores  are  many  small  islands  and 
Dromontories  that  the  waves  havp  thrown  up  (Fis:.  105V 


SHORE  LINES, 


223 


Fig.  390.  —  The  Rock  of  Gibraltar,  from  the  Spanish 
coast,  showing  the  bar  that  joins  it  to  the  main- 
land. 


Another  cause  of  islands  and  promontories  is  the  more  rapid 
work  of  the  waves  in  removing  weak  strata  (p.  211).  Small  islands 
thus  cut  from  the  mainland  are  called  stacks  (Figs.  366,  383). 

The  deposit  of  bars  of  sand  or  pebbles  in  the  protected  water 
behind  islands  often 
ties  them  to  the 
land,  changing  them 
to  promontories 
(Fig.  369).  The  rock 
of  Gibraltar  is  thus 
tied  to  the  mainland 
of  Spain  (Fig.  390), 
and  a  part  of  the  bar 
is  neutral  ground  be- 
tween English  and 
Spanish      territory. 

Sometimes  an  island  -is  tied   by   two  bars,  one  from  each  end, 
inclosing  a  lagoon  between  them. 

Promontories  and  islands  form  irregularities  of  the  coast 
line,  and  are  usually  the  boundaries  of  bays,  or  other  inden- 
tations. Therefore,  the  causes  for  islands  and  promontories 
also  explain  most  of  these  indentations. 

Summary.  —  The  majority  of  islands  and  promontories  are  caused 
by  sinking  of  the  land.  Other  causes  are  mountain  growth,  volcanic 
action,  coral  reef  building,  the  formation  of  barrier  beaches,  the 
growth  of  deltas,  and  the  irregular  cutting  by  ivaves.  Bars  deposited 
behind  islands  often  change  them  to  promontories.  Tliese  causes 
tlso  account  for  most  of  the  bays  and  other  indentations. 

161.  Harbors.  — No  feature  of  the  seacoast  is  more  impor- 
tant than  the  harbors,  or  small  indentations  of  the  coast,  deep 
enough  for  vessels  to  enter,  and  protected  enough  for  them 
to  remain  safe  from  wind  and  wave.  By  far  the  greater 
number  of  harbors  are  caused  by  sinking  of  the  land,  admit- 
ting the  water  into  the  valleys  (Figs.  350,  388,  389) ;  but 
there  are  many  other  causes  for  harbors. 


224  NEW  PHYSICAL   GEOGRAPHY, 

Some,  like  that  of  New  Orleans,  are  on  large  rivers  wher'' 
there  has  been  little  or  no  sinking  ;  others,  like  that  of  Naple.«_ 
occupy  bays  formed  by  mountain  uplift ;  and  still  others,  like 
that  of  Callao,  are  merely  part  of  a  straight  coast  where  an 
island  serves  to  cut  off  the  winds  and  waves.  What  is  the 
cause  for  Galveston  harbor  (p.  214)  ?  There  are  others  of 
similar  origin.  The  lagoon  of  an  atoll  (Fig.  382),  and  a 
volcanic  crater  breached  by  the  sea  (Fig.  234),  may  also  form 
harbors.  Among  other  causes  is  the  work  of  man  ;  for  he  has 
made  many  harbors,  either  by  dredging  shallow  tidal  rivers, 
as  at  Glasgow,  or  by  building  breakwaters  on  harborless 
coasts. 

For  a  harbor  to  be  useful  at  the  present  day,  and  to  become 
the  site  of  a  great  city,  it  must  be  deep  enough  to  admit  large 
vessels.  It  was  partly  because  of  the  shallowness  of  its  har- 
bor that  Salem  was  outstripped  by  its  neighbor  Boston  ;  but, 
of  late,  even  Boston  harbor  has  needed  deepening  and  im- 
provement to  admit  large  modern  ships. 

To  become  the  site  of  a  great  city,  a  harbor  should  also 
have  a  large  area  of  productive  country  tributary  to  it. 
Baltimore,  Pliiladelphia,  New  York,  and  Boston  harbors  are 
open  to  shipment  not  only  from  the  country  round  about, 
but  also  from  the  great  interior ;  and  New  York  owes  its 
superiority  over  tlie  others  largely  to  the  fact  that  it  has 
connection  witli  the  interior  by  water  as  well  as  by  rail.  On 
the  other  hand,  Castine,  Me.,  has  a  better  harbor  than  even 
New  York ;  but  it  is  not  connected  with  an  extensive  pro- 
ductive country,  and  consequently  has  not  developed. 

Harbors,  like  many  other  coast  forms,  are  temporary  affairs. 
If  the  coast  remains  at  one  level,  and  man  does  not  interfere,  bars 
will  grow  across  harbor  mouths  and  they  will  be  slowly  filled  with, 
sediment.  Both  of  these  processes  are  in  operation,  and  it  is 
necessary  to  expend  large  sums  of  money  to  remove  the  deposits. 
This  is  especially  true  on  sandy  coasts,  where  the  waves  and 
currents  find  much  loose  material  to  drift  about.     For  this  reason 


SHORE  LINES.  225 

the  entrance  to  New  York  harbor  is  through  a  long,  tortuous 
channel  dredged  out  amid  shoals  of  sand  drifted  from  the  sandy 
shores  of  Long  Island  and  New  Jersey. 

Summary.  —  A  harbor  is  an  indentation  of  the  coast,  deep  enough 
for  vessels  to  enter  and  yet  be  protected  from  winds  and  waves. 
There  are  numerous  causes  for  harbors,  of  which  sinking  of  the 
land  is  most  important ;  man  also  makes  harbors  by  dredging 
or  by  building  breakwaters.  To  be  the  site  of  a  great  city,  a  harbor 
must  be  deep  enough  for  large  vessels  and  have  an  extensive  area  of 
productive  country  tributary  to  it.  Waves  and  currents  are  tending 
to  seal  up  and  fill  harbors. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  — 142.  Importance  of  Shore  Lines.  —  Centers  of 
industry;  shipping;  charts;  Coast  Survey;  harbor  improvements;  dan 
gers  of  approach;  lighthouses;  light-ships;  fog-horns;  pilots;  buoys; 
life-saving  stations;  summer  resorts. 

143.  The  Seacoast  is  ever  changing.  —  Wave  work,  —  instances ;  deposit, 

—  instance;  effect  of  elevation  ;  of  depression;  the  ever  changing  coast. 

144.  Elevated  Sea-bottom  Coasts.  —  Nature  of  coast;  illustrations; 
unhealthf ulness ;  agriculture;  harbors;  sinking  of  coast ;  sandbars. 

145.  Straight  Mountainous  Coasts.  —  Effect  of  uplift ;  western  America, 

—  straight  coast,  mountains,  narrow  plain,  sea-bottom  slopes;  recent 
uplift;  settlement,  —  few  harbors,  limited  resources,  mountain  barrier. 

146.  Irregular  Mountainous  Coasts.  —  Cause  of  islands  ;  of  peninsulas ; 
sinking  of  crust  between  ranges ;  Mediterranean,  —  cause,  entrance, 
irregular  coast ;  other  large  seas ;  small  irregularities;  sinking  of  coast; 
settlement;  communication  by  land;  navigation;  western  Italy. 

147.  Coasts  of  Drowned  Lands. —  (a)  Resulting  irregularity :  bays  and 
harbors;  instances;  drowned  rivers;  shoals  and  banks;  islands;  penin- 
sulas, (h)  Fiord  coasts:  origin  of  fiords;  instances;  settlement, 
(c)  Regions  of  soft  rock:  effect  on  coast  form;  settlement,  {d)  Im- 
portance of  irregular  coasts :  harbors;  length  of  coast  line;  fishing  and 
navigation;  interior  waterways;  instances.  (e)  Islands:  isolation; 
Newfoundland ;  Great  Britain. 

148.  Wave  and  Tide  Work.  —  Movement  of  fragments  (a)  offshore, 
(h)  alongshore ;  result ;  reasons  for  irregular  coasts ;  straightening  coast. 

149.  Sea  Cliffs.  —  Zone  of  wave  work;  work  of  breakers;  steepness  of 
cliffs,  —  hard  rock,  soft  rock,  height;  chasms;  sea  caves;  limit  to  wave 
work ;  offshore  platform ;  cutting  back  of  land ;  dangers  to  navigation, 

Q 


226  NEW  PHYSICAL   GEOGRAPHY. 

150.  Beaches,  Hooks,  Bars,  etc.  —  Disposition  of  fragments;  quick- 
sands; pocket  beaches;  grinding  of  pebbles;  bars  across  bays;  bars  sup- 
plied from  sea  cliffs  ;  hooks ;  spits ;  cusps. 

151.  Offshore  Bars.  —  Instances;  lagoons;  gaps  in  bars;  closing  of 
gaps;  cause  of  offshore  bars;  effect  of  wind;  destruction  of  bars;  occu- 
pants of  bars ;  cities  on  bars  ;  shoals. 

152.  Sand  Dunes  of  the  Seacoast.  — Location ;  form ;  effect  of  removal 
of  forest;  instances;  encroachment;  uselessness;  Netherlands. 

153.  Salt  Marshes.  —  Location ;  aid  of  plants ;  channels  on  marsh ; 
change  to  dry  land ;  value;  diked  land;  illustrations;  United  States. 

154.  Mangrove  Swamps.  —  Location ;  jungle. 

155.  Coral  Reefs.  —  Favoring  conditions;  differences  among  corals; 
polyps;  abundant  life  in  a  coral  reef  ;  growth  of  reef;  fringing  ^-eef; 
barrier  reef ;  two  causes  for  barrier  reefs ;  Great  Bai'rier  Reef  ;  elevated 
reefs ;  making  of  land ;  Bermudas. 

156.  Atolls.  —  Form ;  lagoon ;  size ;  elevation  ;  cause  of  elevation  ; 
plants,  animals,  and  man ;  two  explanations. 

157.  Lake  Shores.  —  Resemblance  to  ocean  shores;  phenomena  in 
common  ;  absence  of  tides ;  smaller  cliffs ;  eft'ects  of  life. 

158.  Abandoned  Shore  Lines.  —  Lake  shores;  instances;  resemblance 
to  ocean  shore  lines  ;  elevated  sea  shores ;  instances  ;  characteristics. 

159.  Life  History  of  a  Coast  Line.  —  Controlling  conditions;  young 
coast;  changes  in  young  coast;  mature  coast;  consuming  of  land; 
effect  of  weak  rock ;  offshore  bars. 

160.  Islands  and  Promontories.  —  Sinking  of  coast;  mountain  growth : 
volcanoes ;  coral  reefs  ;  barrier  beaches ;  deltas ;  instances  of  each ;  wave 
work;  stacks;  tied  islands;  causes  of  indentations. 

161.  Harbors.  —  (a)  Definition,  (b)  Causes  :  sinking  of  land;  rivers; 
mountain  uplift ;  islands ;  lagoons  behind  barrier  beaches ;  atoll  lagoons ; 
crater  harbors;  work  of  man.  (c)  Sites  of  great  cities:  depth;  tribu- 
tary country ;  illustrations,     (rf)  Sealing  up  of  harbors  :  bars ;  filling 

Questions.  — 142.  For  what  is  the  coast  most  important?  What 
does  the  government  do  to  fit  it  better  for  commerce?  To  warn  sailoi'S 
of  danger  ?     To  protect  them?     Why  is  the  coast  a  summer  resort? 

143.  In  what  different  ways  is  the  coast  changing? 

144.  What  conditions  are  unfavorable  to  the  development  of  elevrjted 
sea-bottom  coasts?     Why  are  the  harbors  so  poor? 

145.  What  are  the  results  of  the  rising  of  long  chains  of  mountains? 
What  is  the  condition  on  the  coast  of  western  South  America?  Why  aro 
such  conditions  unfavorable  to  dense  population  ? 

146.  How  does  mountain  growth  cause  irregular  coasts?  WliaO  aiO 
the  conditions  in  the  Mediterranean  ?    Give  other  instances  of  irregular 


SRORE  LINES.  227 

coasts.     AVhat  is  the  condition  in  Greece  ?     Why  are  such  coasts  favor- 
able to  navigation?     Why  unfavorable  to  dense  settlement? 

147.  What  results  are  produced  by  entrance  of  the  sea  into  valleys  ? 
Give  illustrations.  What  are  .the  results  of  complete  or  partial  submer- 
oence  of  hills  ?  How  do  the  nature  of  the  rock  and  the  vallev  form  iuflu- 
ence  the  coast  outline?  What  effect  has  this  on  settlement?  Why  are 
moderately  low,  irregular  coasts  favorable  to  settlement?  What  effect 
has  sinking  of  the  land  on  island  people  ?     Give  illustrations. 

148.  What  work  are  the  waves  and  currents  doing  ?  What  effect  does 
this  have  on  irregular  coasts  ?     W^hy  are  not  all  coasts  regular? 

149.  How  are  sea  cliffs  formed  ?  How  do  cliffs  in  hard  and  soft  rocks 
differ?  What  effect  has  variation  in  strata?  What  are  the  results  of 
cutting  cliffs  back?     What  effect  has  this  on  navigation? 

150.  What  becomes  of  the  rock  fragments  drifted  along  the  shore? 
How  do  the  materials  vary  ?  What  forms  are  assumed  by  the  beaches 
and  bars  thus  built? 

151.  Describe  the  bars  along  the  Texas  coast.  How  are  they 
formed?     Of  what  importance  are  barrier  beaches? 

152.  W^hat  are  the  characteristics  of  sand  dunes?  What  damage  do 
sand  dunes  accomplish?     What  is  the  condition  in  the  Netherlands? 

153.  Where  are  salt  marshes  formed?  How?  What  is  the  result? 
Of  what  importance  are  salt  marshes? 

154.  What  are  mangrove  swamps  ?    Where  are  they  found  ? 

155.  Under  what  conditions  do  corals  thrive?  How  is  the  coral 
made?  How  do  the  polyps  live?  How  do  the  reefs  grow?  In  what 
two  ways  may  fringing  reefs  be  made?  Describe  the  Great  Barrier 
Reef.     What  is  the  origin  of  the  Bermudas  and  Bahamas? 

156.  What  are  the  characteristics  of  atolls?  Where  are  they  found? 
How  are  they  caused  ? 

157.  Compare  and  contrast  lake  and  sea  shores. 

158.  Give  instances  of  abandoned  lake-shore  lines.  Of  elevated  sea- 
shore lines.     What  is  their  nature  ? 

159.  What  causes  are  there  for  variation  in  the  life  history  of  a  coast 
line  ?  State  the  life  history  of  a  hard  rock,  irregular  coast.  What  differ- 
ences are  there  where  the  rock  is  weak  ? 

160.  State  the  different  causes  for  islands  and  promontories.  Give 
instances  wherever  possible.  How  may  an  island  be  changed  to  a 
promontory?    What  are  the  causes  of  indentations? 

161.  AVhat  is  the  cause  for  most  harbors?  State  other  causes  for  har- 
bors. What  two  factors  are  of  importance  in  determining  the  growth 
of  cities  about  harbors  ?  Give  two  instances.  Why  must  money  be  spent 
to  imorove  harbors? 


228  NEW  PHYSICAL   GEOGRAPHY, 

Suggestions.  —  (1)  Take  some  angular  fragments  of  a  soft  rock,  or 
brick,  and  shake  them  for  a  few  moments  in  a  fruit  jar  containing 
water.  What  causes  the  water  to  become  muddy?  Find  out  how 
marbles  are  rounded.  (2)  In  a  shallow  pan,  mold  an  irregular  land  of 
clay.  Carefully  pour  in  water  until  the  land  is  partly  drowned.  Study 
the  land  forms  produced.  Blow  on  the  water  surface,  causing  the  waves 
to  reach  the  coast  diagonally.  Are  any  bars  formed  ?  Any  other  coast- 
line features?  Study  and  describe  them.  Now  draw  off  some  of  the 
water  to  leave  the  shore  line  elevated.  Describe  the  new  coast  line. 
How  does  it  diifer  from  the  former  ?  Cause  waves  to  attack  it,  and  describe 
the  result.  By  using  care,  and  by  making  the  land  of  materials  varying 
in  hardness,  much  concerning  shore-line  phenomena  may  be  simply  and 
easily  illustrated.  (3)  If  the  school  is  near  the  seashore  or  the  shore  of  a 
lake,  at  least  one  excursion  should  be  made  to  study  shore  phenomena. 
Are  there  beaches?  Where  does  the  material  come  from  ?  Are  there  cljffs  ? 
What  is  happening  there?  Have  any  portions  been  recently  removed 
by  the  waves?  Do  the  bowlders  or  pebbles  show  signs  of  rounding? 
What  is  the  cause?  Where  does  the  finer  ground-up  material  go?  Are 
there  any  mud  flats ?  What  is  the  source  of  the  material?  Ask  some 
fisherman  what  material  covers  the  bottom  offshore.  Are  there  salt 
marshes?  What  are  their  characteristics?  Are  tidal  currents  perform- 
ing any  work  ?  (4)  If  the  school  is  on  a  sea  or  lake  port,  the  harbor 
should  be  studied  ;  its  form  ;  depth  (making  use  of  a  Coast  Survey  map)  ; 
cause  ;  nature  of  bottom ;  improvements  made  ;  others  needed ;  light- 
houses; other  guides  and  aids  to  entrance ;  source  of  principal  materials 
received  for  shipment;  of  principal  imports;  places  to  which  these  are 
distributed;  reasons  for  importance  of  port.  If  not  on  a  harbor,  the 
nearest  large  port  should  be  studied  in  a  similar  way  by  means  of  the 
Coast  Survey  or  Lake  Survey  charts  (see  Appendix  J). 

Reference  Books.  —  Shaler,  Sea  and  Land,  Scribuer's  Sons,  New 
York,  1891,  ^2.50;  Tarr,  Chapter  X,  Pht/sical  Geography  of  New  York 
State,  Macmillan  Co.,  New  York,  1902,  |3.50;  Siialer,  Beaches  and  Tidal 
Marshes  of  the  Atlantic  Coast,  National  Geographic  Monographs,  American 
Book  Co.,  New  York,  1895,  $2.50 ;  Gilbert,  Features  of  Lake  Shores, 
5th  Annual  U.  S.  Geological  Survey,  p.  75 ;  Shaler,  Salt  Marshes,  6th 
Annual  U.  S.  Geological  Survey,  p.  359;  Shaler,  Harbors,  13tii  Annual 
U.  S.  Geological  Survey,  p.  99  ;  Darwix,  Structure  and  Distribution  of 
Coral  Reefs,  Appleton  &  Co.,  New  York,  1889,  $2.00;  Dana,  Corals  and 
Coral  Islands,  Dodd,  Mead  &  Co.,  New  York,  1895,  $5.00. 


CHAPTER   XII. 

THE  ATMOSPHERE. 

162.  Composition  of  the  Air.  —  (A)  Oxygen^  Nitrogen^  and 
Carbon  Dioxide.  —  Until  recently  air  was  believed  to  be  a 
mixture  of  two  gases,  oxygen  (about  21  per  cent)  and  nitro- 
gen (about  79  per  cent).^  Oxyen  is  of  vital  importance  to 
animals,  for  all  breathe  it ;  but  nitrogen,  though  used  by 
some  plants,  is  of  far  less  importance.  It,  however,  increases 
the  bulk  of  the  air  and  dilutes  the  oxygen.  Man  probably 
could  not  live  in  an  atmosphere  of  pure  oxygen,  for  it  would 
cause  too  rapid  changes  in  the  tissues  of  the  body. 

About  0.04  per  cent  of  the  air  is  carbon  dioxide  (often 
called  carbonic  acid  gas),  which,  in  spite  of  its  small  quan- 
tity, is  very  important.  It  is  composed  of  one  part  of  carbon 
and  two  of  oxygen,  and  plants  have  the  power  of  separating 
them,  building  the  carbon  into  their  tissues. 

In  the  bodies  of  animals,  on  the  other  hand,  oxygen  unites 
with  carbon  by  a  process  of  slow  combustion,  and  with  each 
breath  carbon  dioxide  is  returned  to  the  air.  Fire  is  a  more 
rapid  form  of  combustion,  oxygen  combining  with  the  car- 
bon of  the  wood,  coal,  oil,  etc.,  and  forming  carbon  dioxide. 
All  forms  of  combustion,  whether  rapid  or  slow,  produce 
heat.  In  such  rapid  combustion  as  fire,  sufficient  heat  is 
produced  to  do  much  work,  —  for  example,  the  formation 
of  steam,  whose  energy  may  be  used  to  run  locomotives  or 

1  In  1895  a  new  element,  argon,  was  discovered  in  the  atmosphere,  and 
siiice  then  several  other  inert  elements  have  been  found  in  it.  They  re- 
semble nitrogen  so  closely  that,  although  they  are  taken  with  every  breath, 
they  were  never  before  detected. 

229 


230  NEW   PHYSICAL    GEOGRAPHY. 

machinery.     By  slow  combustion  the  necessary  heat  is  pro- 
duced to  form  the  energy  which  animals  need  for  life. 

Summary.  —  The  atmosphere  is  a  mixture  of  gases.  Argon  and 
nitrogen  are  quite  inert ;  carbon  dioxide,  which  exists  in  very  small 
quantities,  is  of  vital  importance  to  plants;  oxygen  is  breathed  by 
\dl  animals,  in  which  it  produces  slow  combustion,  giving  the  neces- 
aary  heat  for  life.     It  also  causes  rapid  combustion  in  fire. 

(B)  Water  Vapor.  —  Vapor  rises  from  all  damp  surfaces 
and  water  bodies ;  that  is,  liquid  water  is  evaporating  or 
changing  to  an  invisible  gas.  This  is  the  reason  why  wet 
clothes  become  dry  when  hung  on  a  line,  and  sidewalks, 
after  a  rain.  The  amount  of  vapor  water  varies  from  place 
to  place,  some  regions  having  very  dry  air,  others  damp  or 
humid  air.  Even  in  the  same  place  the  amount  of  vapor 
differs  from  time  to  time,  some  days  being  humid,  others 
dry.  When  the  air  is  dry,  evaporation  is  rapid  and  the  sky 
clear ;  but  when  there  is  much  vapor,  there  may  be  clouds 
and  rain.  The  condensation  of  this  water  vapor  gives  rise 
to  dew,  frost,  fog,  clouds,  rain,  snow,  and  hail. 

Summary.  —  Invisible  water  vapor,  which  rises  from  water  bodies 
and  damp  surfaces,  is  also  mixed  tcith  the  air,  in  varying  amounts. 

(C)  Dust  Particles.  —  Solid  particles  that  float  in  the  air  are 
called  dust.  Some  of  these  are  whirled  up  from  the  ground  by 
winds ;  some  are  b:ts  of  carbon  from  smoke,  or  pollen  of  plants,  or 
microbes.  Dust  particles  accumulate  around  cities,  causing  a 
dull,  hazy  atmosphere;  but  during  long  periods  of  drought,  or 
wlien  forest  fires  are  burning,  the  air  even  in  the  country  be- 
comes hazy  with  dust.  Rain  washes  dust  from  the  air,  so  that  it 
is  usually  clearer  after  a  rain  storm.  Over  the  ocean,  and  on  high 
mountains,  the  air  is  quite  free  from  dust  particles. 

Dust  is  important  in  furnishing  solid  particles  around  which 
vapor  condenses  to  form  fog  and  rain.  The  microbes  are  drifted 
about  by  the  winds,  thus  helping  to  spread  disease. 

Summary.  —  Particles  of  dust,  smoke,  microbes,  and  other  solids 
often  cause  the  air  to  be  hazy,  especially  near  cities. 


THE  ATMOSPHERE. 


281 


Fig.  391.  —  To  illustrate  the  decrease  in  density  of 
the  atmosphere  from  sea  level  to  higher  regions. 


163.  Effect  of  Gravity.  —  Although  light  and  invisible, 
air  has  perceptible  weight.  One  particle,  drawn  down  by 
p-ravity,  presses  on  those  below  it,  as  stones  in  a  pile  press 
on  those  beneath.  Since  the  air  extends  to  a  height  of  two 
hundred  miles  or  more,  this  great  column  has  a  weight  that 
can  be  measured.  At  sea  level,  its  average  weight  is  15 
pounds  to  every 
square  inch  of  sur- 
face. This  is  equal 
to  a  column  of 
about  30  feet  of 
water,  or  30  inches 
of  mercur3^ 

Since  there  are 
many  square  inches 
on  the  surface  of  a 
human  body,  it  is 
evident  that  each  of  us  bears  a  great  weight  of  air;  but  as  the 
pressure  is  equal,  both  inside  and  out,  we  do  not  notice  it  (p.  181). 
If  this  pressure  were  suddenly  removed  from  the  outside,  the 
expansion  of  the  air  within  our  bodies  would  burst  many  of  the 
tissues. 

Pressure  pushes  the  molecules  of  gases  closer  together;  and, 
therefore,  the  air  is  denser  near  the  earth  than  higher  up  (Fig.  391). 
As  a  result  of  this,  fully  two  thirds  of  the  atmosphere  is  within 
six  miles  of  sea  level;  and  the  air  is  about  half  as  dense  at  the  top 
of  a  high  mountain,  like  Mt.  St.  Elias,  as  at  its  base.  .  The  air  on 
mountain  tops  is  so  thin,  or  rarefied,  that  it  is  difficult  to  breathe 
oxygen  enough  for  the  needs  of  the  body.  Some  men  and  animals 
have  become  accustomed  to  this  rarefied  air  and  are  able  to  live  in 
high  altitudes;  but  a  traveler  from  lower  levels  finds  his  breath- 
ing greatJ}^  quickened  by  the  effort  to  get  enough  oxygen,  and  not 
uncommonly  he  becomes  quite  exhausted. 

Air  is  so  extremely  elastic  that  even  slight  differences  in  tem- 
perature change  its  density  or  weight.  For  example,  the  air 
filling  a  room  10x20x20  feet  weighs  301  pounds  at  60°;    but 


232  NEW  PHYSICAL   GEOGRAPHY. 

when  the  temperature  is  raised  to  80°,  the  air  is  so  expanded  that 
there  are  only  291  pounds  in  the  room. 

The  pull  of  gravity  is  greater  on  heavy  than  on  light  air,  and 
these  differences  in  weight  start  movements  of  the  air,  causing 
winds  (p.  255). 

Summary.  — Air  has  iveiglit,  at  sea  level  about  fifteen  pounds  to 
the  square  inch.  It  is  compressed,  or  more  dense,  at  the  bottom  ;  and 
lighter,  or  more  rarefied,  higher  up.  It  is  very  elastic,  varying  in 
density  with  temperature,  and  being  easily  set  in  motion. 

164.  Light.^  —  A  form  of  energy,  commonly  called  light 
and  heat,  is  emitted  by  bodies  having  a  high  temperature  ; 
for  example,  burning  coal,  red-hot  iron,  and  the  white-hot 
sun.  This  energy  travels  at  great  speed,  crossing  the 
93,000,000  miles  which  separates  earth  and  sun  in  about  8 
minutes. 

Tlie  sunlight  which  comes  to  us  is  made  of  a  series  of  waves, 
differing  in  length  and  color,  whose  union  forms  white  light. 
If  a  beam  of  sunlight  is  allowed  to  pass  through  a  three- 
cornered  glass  prism  these  waves  are  turned,  each  at  a  slightly 
different  angle.  The  beam  enters  as  white  light,  but  comes 
out  with  the  color  Avaves  separated,  among  which  violet, 
indigo,  blue,  green,  yellow,  orange,  and  red  may  be  recog- 
nized. This  bending  of  light  rays  is  called  refraction;  the 
colors  are  called  the  colors  of  the  spectrum.,  or  of  the  rainbow. 

Some  of  the  rays  that  reach  a  body  pass  away  from  it,  or 
are  reflected.  This  is  especially  true  of  smooth  surfaces, 
like  water,  or  the  glass  of  a  mirror  ;  but  it  is  true  even  of  ir- 
regular surfaces,  like  the  ground.  It  is  reflected  sunlight 
that  makes  the  moon  and  planets  appear  light ;  and  the  earth 
would  have  the  same  appearance  if  seen  from  them. 

Refraction  and  reflection  cause  many  changes  in  light  as  it 
passes  through  the  atmosphere.     Mirage  is  caused  by  reflection 

^  A  thorough  study  of  the  nature  and  behavior  of  light  belongs  to  physics  i 
but  the  student  of  physical  geography  should  understand  the  main  reasons 
ior  the  color  phenomena  of  the  atmosphere. 


THE  ATMOSPHERE,  233 

«vhen  layers  of  air  have  different  temperatures  and,  conse- 
quently, different  densities.  It  is  especially  perfect  in  deserts 
and  on  the  sea,  commonly  showing  objects  inverted  —  a  vessel 
with  the  masts  downward,  for  instance.  In  deserts  mirage  causes 
an  appearance  of  water  which  is  often  very  deceptive. 

Rainbows  are  caused  by  refraction  of  light  in  its  passage  through 
raindrops,  and  reflection  of  the  spectrum  colors  thus  produced. 
The  halos  around  sun  and  moon  are  due  to  similar  changes  in  the 
light  rays,  in  their  passage  through  the  ice  crystals  of  thin,  fleecy 
clouds  high  in  the  air. 

The  colors  of  leaves,  flowers,  and  other  objects  are  due  to  reflec- 
tion. When  light  reaches  some  objects,  for  example  white 
paper,  all  the  waves  are  reflected  and  the  paper  appears  white. 
Other  objects,  like  black  cloth,  reflect  very  little  light,  the  rays 
being  absorbed.  Still  other  objects  absorb  some  of  the  waves 
and  reflect  others,  thus  giving  color.  A  red  flower,  for  instance, 
reflects  an  excess  of  red  waves ;  and  green  leaves,  green  waves. 

Diffraction,  or  selective  scattering,  is  an  important  cause  for  color 
effect  in  the  sky.  Dust  in  the  air  interferes  with  the  passage  of 
light  waves,  as  small  pebbles  in  shallow  water  interfere  with 
water  waves.  By  this  interference,  some  of  the  waves  that 
make  the  white  light  are  turned  aside,  or  scattered.  The  weaves 
having  the  shortest  length,  or  those  on  the  violet  end  of  the 
spectrum,  are  most  easily  turned  aside ;  that  is,  they  are  selected 
for  scattering. 

The  blue  color  of  the  sky  is  due  to  the  selective  scattering 
of  the  short  blue  waves.  When  there  is  much  dust  in  the  air, 
the  longer  red  and  yellow  rays  are  scattered,  giving  red  and 
yellow  colors  to  the  sky.  These  colors  are  especially  common 
at  sunrise  and  sunset,  when  the  rays  pass  for  a  long  distance 
through  the  lower  dust-filled  layers  of  the  air  (Fig.  392).  The 
varied  cloud  colors  of  sunrise  and  sunset  are  the  result  of  reflection 
of  colors  caused  by  refraction  and  diffraction. 

Summary.  —  Wliite  light  is  made  by  the  uyiion  of  a  number  of 
ivaves  of  different  length,  ivhich,  tvhen  separated  by  refraction,  give 
the  colors  of  the  spectrum.  These  colors  may  be  reflected,  as  in  col- 
ored objects,  rainbows,  halos,  and  clouds  at  sunset.     The  scattering. 


234  NEW  PBYSICAL   GEOGBAPHT, 

or  diffraction^  of  waves  by  the  interference  of  dust  gives  the  blue 
color  to  the  sky  and  the  reds  and  yellows  of  sunrise  and  sunset. 

165.  Heat.  —  (A)  Radiant  Energy.  —  On  approaching  a 
hot  stove  one  feels  its  warmth,  even  at  a  distance  of  several 
feet.  Waves  of  heat  from  the  stove  have  passed  that  distance 
through  the  air.  If  the  stove  is  very  hot,  the  cover  may  be 
red  ;  then  the  waves  from  it  produce  not  only  heat,  but  the 
sensation  of  light  on  the  eye.  This  form  of  energy,  which 
we  call  heat  and  light,  is  known  as  radiant  energy^  and  the 
process  of  emitting  it  is  called  radiation.  The  greatest  well- 
known  center  of  radiant  energy  is  the  sun  ;  but  doubtless 
some  of  the  stars  are  still  larger  and  hotter,  though  so  far 
away  that  they  do  not  influence  us. 

Radiation  causes  a  loss  of  heat,  and  by  it  bodies  grow 
cooler  ;  thus,  in  a  few  hours,  a  stove  with  the  fire  out  will 
radiate  all  its  heat  and  become  cold.  The  sun  is  also  losing 
heat,  radiating  it  outward  in  all  directions  ;  but  millions  of 
years  will  be  required  for  so  large  and  hot  a  body  as  the 
sun  to  grow  cold.  A  very  small  proportion  of  the  heat  radi- 
ated from  the  sun  is  intercepted  by  the  earth  (Fig.  15), 
where  it  causes  many  important  effects. 

Summary.  —  Hadiant  energy,  heat  ayid  light,  which  is  emitted 
from  hot  bodies,  is  being  radiated  in  all  directions  from  the  sun, 
which  is,  therefore,  slowly  growing  cooler. 

(B)  Passage  of  Radiant  Energy.  —  Certain  substances,  like 
glass  and  the  gases  of  the  air,  allow  light  to  pass  so  freely 
that  they  are  said  to  be  transparent.  They  also  allow  heat 
to  pass  freely,  or  are  diathermanoiis.  For  this  reason,  not- 
withstanding the  thickness  of  the  atmosphere,  the  sun's  rays 
at  midday  reach  the  earth's  surface  with  little  change. 

Dust  particles  interfere  with  the  passage  of  light  rays,  as 
we  have  seen  ;  and,  in  much  the  same  way,  they  interfere  with 
the  passage  of  heat.  This  is  clearly  proved  by  the  differ- 
ence in  brightness  and  warmth  of  the  sun  at  midday  and 


THE  ATMOSPHERE,  "Z^O 

late  in  the  afternoon;  for  we  may  often  actually  look  at  the 
setting  sun.  At  that  time  many  of  the  rays  are  intercepted 
in  their  passage  through  the  great  thickness  of  dust-laden 
air  nea:*  ^he  surface  (Fig.  392). 

Summary.  —  Air  and  other  substances  transparent  to  light  allow 
heat  to  freely  pass,  or  are  diatherinanous.  Hie  interference  of  dust 
greatly  lessens  the  sun'' s  power  ivhen  it  low  is  in  the  heavens. 

(C)  Radiation  from  the  Earth.  —  Bodies  that  are  warmer 
than  their  surroundings  emit  waves  of  radiant  energy. 
The  earth  itself  is  radiating  into  space  the  heat  that  comes 
to  it  from  the  sun;  if  this  were  not  so,  it  would  grow 
warmer*  and  warmer.  During  the  day  more  heat  comes 
than  can  be  radiated;  but  at  night,  when  the  sun's  rays  are 
cut  off,  radiation  cools  the  ground.  In  summer,  when  the 
days  are  longer  than  the  nights,  the  ground  grows  steadily 
warmer;  but  in  winter,  when  the  days  are  short  and  the 
sun  low  in  the  heavens,  radiation  is  so  far  in  excess  of  the 
supply  of  heat  that  the  ground  becomes  cold. 

Some  bodies  are  much  better  radiators  than  others.  Rocks  and 
earth  radiate  heat  better  than  water,  and  hence  cool  more  quickly. 
This  is  one  reason  why,  in  winter,  the  land  becomes  colder  than 
the  water.  On  cold  nights  those  objects  that  radiate  their  heat 
most  quickly  have  most  frost.  Perhaps  you  can  observe  this 
difference  early  some  frosty  morning. 

Summary.  —  The  earth  is  always  radiating  heat,  and  this  is  ichy 
it  becomes  cool  or  cold  at  night  and  in  winte7\  Some  objects,  like 
water,  are  poorer  radiators  than  others,  like  the  ground. 

(D)  Reflection  and  Absorption.  — Bodies  that  reflect  light 
also  reflect  heat.  Water,  for  example,  reflects  a  large  per- 
centage of  the  rays  that  reach  its  surface,  and  this  is  why 
one  becomes  sun-burned  so  easily  on  water.  Quarries  and 
city  streets  are  warmer  than  the  open  country,  partly  be- 
cause the  sun's  rays  are  reflected  from  their  walls. 


236  NEW  PHYSICAL   GEOGRAPHY, 

Some  bodies  reflect  little,  the  sun's  rays  being  used  mainly  in 
warming  them.  Such  bodies  are  said  to  absorb  heat.  This  is 
especially  true  of  black  objects,  while  white  objects  reflect; 
therefore  white  clothing  is  cooler  than  black.  This  can  be  readily 
proved  in  winter  by  placing  two  pieces  of  cloth,  one  black,  the 
other  white,  on  a  bank  of  snow  in  the  sunlight.  The  black  cloth 
soon  sinks  into  the  snow  because  the  sun  warms  it,  while  the 
white  cloth  remains  at  the  surface. 

Summary.  —  Some  bodies,  such  as  ivater  and  wJiite  objects,  reflect 
much  heat;  others,  such  as  black  objects,  absorb  heat  and,  therefore, 
warm  more  rapidly. 

(E)  Conduction.  —  With  a  fire  inside  of  it  a  stove  becomes 
warm  ;  and  an  iron  placed  on  the  stove,  is  also  heated.  In 
this  case  heat  from  the  fire  is  transmitted,  or  conducted, 
through  the  stove.  In  the  same  way,  some  of  the  sun's  heat 
is  conducted  below  the  surface  of  the  water  or  ground,  and 
some  of  it  into  the  air  which  rests  on  these;  but  water,  air, 
and  ground  are  not  so  good  conductors  as  iron.  The 
ground  is  so  poor  a  conductor  that,  at  a  depth  of  from  ten  to 
twenty  feet,  there  is  practically  no  difference  in  temperature 
from  summer  to  winter. 

Summary.  —  Heat  is  transmitted,  or  conducted,  into  the  ivater  and 
ground,  a^id  from  these  into  the  air,  but  air,  ivater,  and  ground  are 
cdl  poor  conductors, 

(F)  Convection.  —  The  lower  layers  of  water  in  a  kettle  on 
a  stove  are  warmed  by  conduction.  Warm  water  is  lighter 
than  cooler  water,  and,  since  gravity  tends  to  draw  the  heavy 
water  to  the  bottom,  these  warm  lower  layers  cannot  stay 
there.  They  are,  therefore,  crowded  up  by  the  settling  of  the 
cooler  layers  from  above.  This  is  convection,  and,  if  the 
water  continues  to  warm,  boiling  finally  takes  place. 

Similar  convection  occurs  in  air  warmed  by  a  lamp.  As 
fast  as  it  is  warmed  near  the  lamp  it  grows  lighter  and 
is  pushed  up  by  heavier  surrounding  air.     The  movement 


THE  ATMOSPHERE,  237 

of  heavier  air  to  crowd  up  warm  air  is  what  causes  the  draft 
'n  a  fire  ;  and  the  crowding  upward  of  the  warm  air  is  what 
\;auses  it  to  go  up  the'  chimney. 

Heat  from  the  sun  is  the  cause  for  very  extensive  convec- 
tion of  the  air  in  all  parts  of  the  earth.  Warmed  in  one 
place,  usually  by  conduction  of  heat  from  the  ground  or 
water,  the  warm  light  air  is  pushed  away  by  heavier  air 
drawn  down  by  gravity.     This  is  the  cause  of  winds  (p.  255). 

Summary.  —  Heat  makes  both  water  and  air  lighter;  and  gravity ^ 
by  drawing  doion  heavier  air,  causes  a  rising,  or  convection,  of  the 
warmer  lower  layers.      Winds  are  thus  caused. 

166.  Warming  of  Land,  Water,  and  Air.  —  (A)  The  Lands. 
—  The  lands  are  warmed  by  absorption  during  the  day,  and 
some  of  the  heat  is  conducted  into  tlie  ground,  warming  the 
upper  few  feet  into  which  the  roots  of  plants  reach.  The 
ground  nowhere  becomes  excessively  warm,  because  much  of 
the  heat  is  lost  by  reflection,  by  radiation,  and  by  conduc- 
tion into  the  air.  Everywhere  the  ground  warms  during  a 
hot,  sunny  day,  and  cools  by  radiation  at  night. 

In  the  tropical  zone  the  ground  does  not  become  very  cool 
at  night,  because  radiation  is  unable  to  remove  all  the  heat 
that  comes  during  the  long,  hot  days.  A  similar  condition 
--^ists  during  summer  in  the  temperate  zones  ;  but,  in  winter, 
radiation  during  the  long  nights  so  chills  the  ground  that  it 
freezes.  In  the  frigid  zones,  radiation  during  the  long  winter 
causes  the  ground  to  freeze  to  depths  of  hundreds  of  feet, 
and  the  short,  cool  summer  supplies  only  heat  enough  to 
melt  the  upper  two  or  three  feet. 

There  are  other  differences  in  the  warming  of  the  lands.  For 
example,  dark-colored  surfaces  warm  more  quickly  than  light, 
and  bare  earth  more  quickly  than  that  covered  by  vegetation. 
There  are  also  differences  according  to  exposure ;  for  instance, 
between  shady  north  slopes  and  sunny  south  slopes,  and  between 
hilltops  and  valleys,  whose  sides  reflect  heat  into  the  valley  and 
also  interfere  with  winds  and  with  radiatiou. 


2J5«  NEW  PHYSICAL   GEOGRAPHY, 

Summary.  —  TJie  lands  are  warmed  by  ahsoi'ption  and  cooled  b^ 
reflection,  conduction,  and  radiation.  The  effect  of  sun^s  heat  variea 
in  different  zones;  also  according  to  the  color  of  the  surface,  the 
cover  of  vegetation,  and  the  exposure. 

(B)  The  Waters.  —  It  is  a  well-known  fact  that  water 
warms  less  quickly  than  land.  There  are  several  reasons  for 
this.  (1)  Water  reflects  heat  more  readily  than  land,  and, 
consequently,  there  is  less  heat  to  warm  it.  (2)  When  one  part 
is  warmed  more  than  another,  it  is  set  in  motion,  so  that  there 
is  a  tendency  for  the  heat  to  be  distributed.  (3)  Water  is 
so  transparent  that,  unlike  ground,  some  of  the  rays  pass  into 
it,  warming  layers  below  the  surface.  Sunlight  penetrates, 
though  dimly,  to  depths  of  several  hundred  feet.  (4)  Twice 
as  much  heat  is  required  to  raise  the  temperature  of  a  pound 
of  water  one  degree  as  of  an  equal  quantity  of  rock.  Some 
of  the  heat  is  expended  in  evaporating  the  water,  and  this  is 
called  "  latent  heat,"  or  heat  of  vaporization. 

It  is  for  these  reasons  that  even  a  small  body  of  water 
warms  more  slowly  during  the  day,  and  during  summer,  than 
the  neighboring  land  (p.  165).  At  night-time  and  in  win- 
ter, on  the  other  hand,  because  it  is  a  very  poor  radiator, 
water  cools  more  slowly  than  land.  Therefore,  from  day  to 
night,  and  from  summer  to  winter,  there  is  slight  range  of 
temperature  in  large  water  bodies,  and  the  climate  over  them 
is  far  less  extreme  than  over  land.  A  climate  with  such 
slight  changes  of  temperature  is  called  equable. 

Summary.  — •  Water  warms  more  sloivly  than  land  because  it 
reflects  more  heat,  is  movable,  is  transparent,  and  some  of  its  heat  is 
expended  in  evaporation.  It  cools  more  sloivly  because  it  is  a  poorer 
radiator.     TJierefore  near  large  water  bodies  the  climate  is  equable. 

(C)  The  Air. — The  air  is  not  perfectly  diathermanous. 
Therefore,  some  of  the  sun's  rays,  and  some  of  the  heat  rays 
radiated  from  the  earth,  are  intercepted  in  their  passage 
through   the    atniosphere-     Dust   is   especially  effective    in 


THE  ATMOSPUliUE. 


239 


intercepting  heat  waves  (p.  234).  A  still  more  important 
cause  for  the  warming  of  air  is  conduction  from  the  ground 
to  the  lower  layers,  which,  being  lighter,  are  then  forced  to 
rise  by  convection.  In  the  same  way  a  stove  warms  the  air 
in  a  room,  by  radiation,  conduction,  and  convection.  At 
night  and  in  winter  the  air  cools  by  radiation  ;  and  contact 
with  the  ground  is  another  important  cause  for  cooling. 

Vapor  and  dust  interfere  with  radiation,  and  for  this  reason 
more  heat  is  retained  in  the  lower  atmosphere  on  hazy  and 
muggy  days  than  in  clear,  dry  weather.  At  such  times  radiation 
fails  to  cool  the  ground,  and  a  hot,  muggy  day  may  be  followed 
by  an  oppressive,  almost  stifling  night.  It  is  under  such  condi- 
tions that  our  most  oppressive  summer  weather  comes. 

Summary  —  Tlie  air  is  warmed  someichat  by  the  nassaqe  of  heat 
rays  through  it,  but  far  more  by  conduction  from  the  j  'ound,  and  by 
convection.  It  is  cooled  by  radiation,  and  by  condttcMon  from  the 
ground.      Vapor  and  dust  interfere  ivith  radiation. 

167.    Causes  for  Differences  in  Temperature  on  the  Earth.  — 

(A)  Position  of  Sun.  —  The 
sun  is  higher  in  the  heavens  at 
noon  than  in  early  morning 
and  late  afternoon  ;  in  sum- 
mer than  in  winter  ;  and  in 
tropical  than  in  temperate 
zones.  When  low  in  the 
heavenj,  the  sun's  power  is 
less  than  when  high,  because 
(1)  the  rays  pass  through  a 
great  thickness  of  dust-laden 
air  when  the  sun  is  low  (Figs. 
392,  394)  and  (2)  fewer  rays 
then  reach  a  given  surface 
(Fig.  393). 

There  are  three  important  results  of  these  different  posi- 
tions of  the  sun.     (1)  Every  day,  as  the  angle  at  which  the 


eUN'S  RAYS  IN 


tATE  AFTERNOON 


SUN'S  RAYS  IN 


EARLY  MORNING 


Fig.  392.  —To  show  that  the  sun's 
rays  pass  through  more  air  when 
the  sun  is  low  in  the  heavens  than 
when  it  is  high. 


240 


NEW'  PHYSICAL   GEOGRAPHY, 


SUN'S  PAYS 

REACHrNG   EARTH  SUN'^   RAYS   REACHING   EARTH   IN 

AT   NOON    FROM  AFTSROON   WHEN   SUN    IS   LOW   IM 

NEARLY   ABOVE  ,                         HEAVENS. 


SURFACE   OF   THE    EAR1  H     <S 

i'lG.   393.  —  Two   bundles   of    rays    having 


sun  s  rays  pask 
through  the  air 
varies  (Fig.  392), 
the  amount  of  heat 
given  out  by  them 
varies.  (2)  As 
the     sun 


changes 


the    same 

width  (AB  and  IJF)  ;  but,  owing  to  the  difference 

in  angle    at   which   they  reach  the  surface    CH,  position,  from  hio'h 

those    that    are    inclined    cover    about    twice    as   •       .-i        -i     ^ 

much  ground  as  those  that  come  straight  down  ^^^    ^'^^    Ueavens    tO 

from  above.     Therefore,  on  the  same  area  there  lower,   the    seaSOns 

are  about  half  as  many  mclined  rays  as  vertical.       ^f    o  n  rvi  r%^  /=i  >.    o  t^  /I 

u  i    o  u.  Ill  111  c  1    a  n  (.1 

winter  occur  in  both  hemispheres.      (3)  AVhere  the  sun  vs 

highest,  that  is  in  the  tropical  zone,  the  climate  is  hottest; 

and  the  climate  grows  cooler  away  from  the  equator  as  the 

sun  gets  lower  in  the  heavens  (Fig.  394). 

Summary.  —  When  the  sun  is  low  in  the  heavens  it  warms  less 
than  when  high,  because  (1)  the  rays  pass  through  so  much  air,  and  (2) 
fewer  rays  reach  a  given 
area.  Changes  in  the  sun^s 
jjosition  in  the  heavens  from 
morning  to  night,  from  sea- 
son to  season,  and  from 
place  toj)lace,  therefore  cause 
differences  in  temperature. 

(B)  Altitude.  —  Obser- 
vations on  mountains  and 
in  balloons  show  that,  as 
the  elevation  increases, 
there  is  a  gradual  de- 
crease in  temperature  at 
the  rate  of  about  1°  for 
every  300  feet.  There  is  no  warm  ground  to  impart  heat  ti, 
these  upper  layers  of  the  atmosphere  ;  and  warm  air,  rising 
from  the  surface,  expands  and  cools  as  it  rises.  Because  the 
upper  air  is  so  cool,  a  frigid  climate  is  found  at  the  equator 


Fig.  394.  —  To  show  that  near  the  poles  the 
sun's  rays  reach  the  earth  in  a  more 
slanting  way,  and  after  passing  through 
more  air,  than  at  the  equator. 


THE  ATMOSPHERE, 


^41 


at  a  height  of  a  few  miles;  and  highlands  are  everj^where 
cooler  than  neighboring  lowlands. 

That  air  cools  on  expanding  may  be  proved  by  a  bicycle  pump. 
Air  pumped  into  the  tire  is  compressed,  or  made  more  dense,  and 
therefore  warmed.  When  this  compressed  air  is  allowed  to 
escape,  it  expands  and  cools,  and  its  coolness  may  be  felt. 

Although  surrounded  by  cold  air,  parts  of  highlands  exposed 
to  direct  rays  of  the  sun  may  become  quite  warm  at  midday. 
On  a  high  mountain  one  may,  therefore,  be  very  warm  in  a  pro- 
tected, sunny  place,  while  a  few  feet  away,  in  a  shady  spot,  or 
one  exposed  to  the  wind,  it  is  very  cold.  Radiation  is  so  rapid 
in  the  clear,  thin,  upper  layers  of  air  that  even  the  warm  places 
quickly  cool  off  when  the  sun  disappears ;  in  fact,  the  temperature 
may  rise  to  90°  at  midday  and  descend  to  10°  at  night. 

Summary.  — Highlands  are  coole:  than  loidands,  the  temperature 
changing  about  1°  for  every  300  ftet.  There  is  no  warm  land  to 
warm  the  upper  air,  and  air  cools  as  it  rises  and  expands.  Rapid 
radiation  in  the  clear,  thin  air  causes  cold  nights. 

(C)  Other  Reasons  for  Differences.  —  We  have  already  learned 
several  reasons  for  differences  in  temperature  according  to  situa- 
tion; for  example,  nature  of  rock,  exposure  (p.  237),  and  influ- 
ence of  water  bodies  (p.  238).  The  nature  and  direction  of  the 
wind  also  influence  temperature  (p.  265).  These  causes  for  dif- 
ferences in  temperature  are  more  fully  studied  in  Chapter  XIV. 

168.     Daily    and    Seasonal 
Temperature    Changes. — 

(A)  Daily  Range.  —  The 
warmest  period  is  not  mid- 
day, when  the  sun  is  high- 
est, but  two  or  three  hours 
after  noon  (Fig.  395).  The 
reason  for  this  is  that  in  the 
morning  it  is  first  necessary 
to  warm  the  ground  that  was  cooled  by  radiation  the  night  be- 
fore.    After  the  ground  is  warmed,  the  tecnperature  continues 

B 


A. 

M. 

P. 

M. 

M        2468       10      12      2468       10      Mf 

23° 
25' 
24' 
23' 
22° 
?1' 
^20° 
19° 
18° 
17° 

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v.. 

/ 

s 

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/ 

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k 

X^ 

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X 

S 



/ 

FEB.  19,1893  ITHACA 

Fig.   395.  —  Normal   daily  temperature 
range  in  winter  at  Ithaca,  N.Y 


242 


NEW  PHYSICAL   GEOGRAPHY. 


o 

too 

96° 
90^ 
86° 
80° 
75° 
70° 
65° 
60° 
66° 

NOON 

NOON 

NOON 

NOON 

NOON 

NOOK 

100° 

95" 

90" 

85° 

80° 

70° 
65" 
60" 
55° 

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Fig.  396.  —  Change  in  temperature  for  six  successive  summer  days  at  Ithaca,  N.Y. 

to  rise  until  the  sun  has  sunk  so  low  that  heat  is  radiated 

away  faster  than  it  is  received. 
Then  the  ground  and  air 
commence  to  cool,  continuing 
to  do  so  until  sunrise.  There- 
fore the  coldest  period  is  not 
midnight,  but  just  before  sun- 
rise (Fig.  395).  Because  of 
these  conditions  there  is  a  nor- 
mal daily  change,  or  range,  of 
temperature  similar  to  tliat 
shown  in  the  diagram  (Fig. 
395). 

There  are  a  number  of  condi- 
tions which  may  occasionally  in- 
terfere with  the  normal  daily 
range  (Fig.  396).  A  cloudy  sky, 
interfering  with  the  passage  of 
the  sun's  rays,  may  prevent  the 
temperature  from  rising  after 
noon ;  or  winds  may  bring  air 
so  cold  that  the  temperature 
falls,  even  during  the  daytime ; 
or  warm  winds  may  cause  the 
temperature  to  rise  throughout 
the  night. 

The  amount  of   change  from 


M         3    A.M.        F                9          NOON          ".6                9     P.M. 

0 
100 

0 

90 

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70 

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60 

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I'iG.  397.  —  Normal  summer  (heavy 
line)  and  winter  (dotted  line)  daily 
temperature  range  for  several 
places.  (1)  Arctic  ;  (2)  St.  Vin- 
cent, Minn.  ;  (3)  Djarling,  India  ; 
(4)  Jacobabad,  India  ;  (5)  Key 
West,  Fla. ;  (G)  Galle,  India;  Sand 
6  are  near  the  warm  ocean. 


THE  ATMOSPHERE. 


243 


day  to  night  differs  from  time  to  time  and  from  place  to  placa 
Thus  the  range  is  great  when  warm  days  are  followed  by  cool 
nights,  and  less  when  cool  days  are  followed  by  cool  nights.  The 
daily  range  in  winter  is  quite  different  from  that  in  summer ;  it 
is  different  at  the  equator  from  what  it  is  in  temperate  latitudes ; 
and  on  the  land  from  what  it  is  at  sea  (Fig.  397). 

Summary.  —  In  the  normal  daily  range  the  temperature  is  highest 
after  midday,  and  lowest  just  before  sunrise.  The  amount  of  daily 
range  varies  from  time  to  time  and  from  place  to  place. 

(B)  Seasonal  Range.  —  The  yearif^  range  of  temperature 
closely  resembles  the  daily  range.  If  the  average  tempera- 
ture for  each  day  is  kept, 
it  will  be  found  that  in 
the  northern  hemisphere 
there  is  a  steady  rise  from 
March  to  August,  and 
then  a  gradual  fall  until 
February  (Fig.  398).  The 
reason  why  the  coldest 
weather  comes  after  mid- 
winter (December  21)  is 
that  radiation  continues 
to  cool  the  ground  and 
air  until  the  days  become 
long  enough,  and  the  sun 
high  enough,  to  overbal- 
ance the  effect  of  radia- 
tion. The  hottest  period 
of  the  year  comes  after 
midsummer  (June  21), 
for  the  same  reason  that  the  hottest  time  of  day  is  after  noon. 

While  there  is  a  normal  seasonal  curve  as  described,  it  differs 
greatly  in  various  parts  of  the  world  (Fig.  398).  For  example, 
the  midwinter  temperature  at  the  equator  is  very  high,  in  the 
frigid  zones  very  low;  the  range  over  the  equable  ocean  is  far  less 


Fig.  398.  —  Seasonal  temperature  range  in 
several  places.  (1)  St.  Vim-ent,  Minn. ; 
(2)  New  York  State ;  (3)  Yuma,  Ariz. ; 
(4)  Key  West,  Fla. ;  (5)  Galle,  India;  4 
and  5  are  near  the  equable  ocean. 


244  NEW  PHYSICAL    GEOGRAPHY. 

than  that  over  the  land ;  in  the  southern  hemisphere  the  lowest 
temperature  comes  at  the  time  of  our  summer.  There  are  also 
differences  caused  by  altitude,  deserts,  and  other  influences. 

Summary. —  TJie  average  temperature  rises  until  after  midsum- 
mer and  descends  until  after  midwinter.  The  normal  curve  of 
seasonal  temperature  range  varies  from  place  to  place. 

FORMS   OF   WATER. 

169.  Humidity.  —  Water  vapor,  which  rises  from  the  ocean, 
and  all  damp  surfaces  (p.  230),  is  dilTused  through  the  air 
and  drifted  about  with  it.  It  finds  its  way  to  all  parts  of  the 
earth;  not  even  the  Sahara  has  absolutely  dry  air.  The 
actual  amount  of  vapor  in  the  air,  that  is,  the  amount  in 
pounds  or  quarts,  is  known  as  the  absolute  humidity.  If 
there  is  as  much  as  possible,  the  air  is  said  to  be  saturated. 
For  example,  in  a  room  10  x  20  x  20  feet,  the  air  at  a  tem- 
perature of  80°,  if  saturated,  has  Q\  pounds  of  water  in  the 
form  of  vapor.     This  is  its  absolute  humidity. 

To  represent  the  amount  of  vapor  present  in  air,  com- 
pared with  the  amount  that  might  be  there,  the  term  relative 
humidity  is  employed.  Relative  humidity  is  measured  in 
percentages.  Thus  the  relative  humidity  of  saturated  air  is 
100  per  cent,  for  it  has  all  it  can  contain ;  of  absolutely  dry 
air,  0  per  cent ;  and  of  air  having  only  half  as  much  as  it 
might  carry,  50  per  cent. 

If  the  relative  humidity  is  low,  as  in  deserts,  there  is  a 
chance  for  so  much  more  vapor  in  the  dry  air  that  evapora- 
tion is  rapid ;  if  the  humidity  is  high,  as  in  the  tropical  forest, 
there  can  be  little  evaporation,  and  surfaces  remain  damp. 
We  notice  this  difference  in  summer,  for  some  days  are  clear 
and  dry,  others  are  humid  or  muggy.  When  the  humidity 
is  great,  the  weather  is  most  oppressive ;  we  perspire  easily, 
and  are  very  uncomfortable,  because  there  can  be  little 
evai;)oration  from  the  surface  of  the  body. 


MONDAY 

TUESDAY 

WEDNbSDAY 

THURSDAY 

FRIDAY 

SATURDAY 

SUNDAY 

6         XII      6 

6       XII     6 

6        XII      6 

6       XII       6 

6       XII      6 

6       XII       6 

6       XII      6 



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80 
60 
40 
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AUG. 14  15  16  17  18  19  AUG. 20  1893 

Fig.  391). — Daily  changes  in  relative  humidity  at  Ithaca,  N.Y.,  for  one  week.  Notice 
that  at  night  the  humidity  rises  nearly  or  quite  to  the  dew  point  (100  per  cent),  but 
in  the  warmest  part  of  the  day  is  very  low.  This  does  notanean  any  change  ic 
the  absolute  humidity,  but  is  the  result  of  changes  in  temperature  from  day  to  night 


Fig.  400.  —  Above  the  clouds,  mountain  tops  projecting  through. 


Fig.  401.  —  Clouds  forming  on  a  mountain  side.    Damp  winds  blowing  upon  the 
cold  mountain  slopes  are  here  chilled  until  the  dew  point  is  reached. 


09 

3 


0; 


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THE  ATMOSPHERE.  245 

Warm  air  can  carry  more  water  vapor  than  cool  air,  for 
the  amount  of  vapor  possible  depends  on  temperature.  For 
this  reason,  when  the  temperature  in  the  room  mentioned 
above  is  60°  there  can  be  only  S^  pounds  of  water  vapor  in 
the  air.  There  is,  therefore,  far  less  vapor  in  the  frigid  than 
in  the  tropical  zone. 

From  this  it  is  evident  that  if  saturated  air  is  warmed,  it 
ceases  to  be  saturated  ;  that  is,  its  relative  humidity  falls 
(Fig.  399)  and  evaporation  is  possible.  This  is  illustrated 
by  the  Sahara.  There  the  winds  are  blowing  toward  a 
warmer  region,  and  the  relative  iiumidity  is  being  constantly 
lowered,  making  the  air  so  dry  that  the  ground  is  dried  and  a 
desert  produced.  If,  on  the  other  hand,  damp  air  is  cooled, 
its  relative  humidity  increases,  and  the  point  is  soon  reached 
when  it  becomes  saturated.  Further  cooling  then  forces 
some  of  the  vapor  to  condense  to  liquid  water,  or,  if  the  tem- 
perature is  below  freezing,  to  snow  or  ice.  This  is  known 
as  precipitation. 

These  facts  explain  many  phenomena.  Thus,  when  one 
breathes  against  a  cool  window  pane  the  breath  is  cooled  to 
the  point  of  saturation,  and  some  of  the  vapor  caused  to  con- 
dense. A  glass  of  water  "  sweats  "  on  warm,  muggy  days, 
because  the  cool  glass  reduces  the  temperature  of  the  air  near 
it,  and  raises  the  relative  humidity  to  the  point  of  saturation. 
Then  some  of  the  vapor  must  condense.  This  point  of 
saturation  is  often  called  the  "dew  point,"  because,  when  it 
is  reached,  dew  forms  on  the  ground.  Precipitation  is 
caused  whenever  the  air  is  chilled  to  the  dew  point. 

Summary.  —  Absolute  humidity  is  the  actual  amount  of  ivater 
vapor  in  the  air  at  a  given  time;  relative  humidity  is  the  j^ercentage 
present  compared  to  what  might  he  present  at  that  temperature.  The 
relative  humidity  decreases  icith  rising  temperature,  and  increases 
with  falling  temperature.  When  it  decreases,  evaporation  becomes 
more  rajyid;  ichen  it  increases,  if  it  reaches  the  point  of  saturation, 
or  the  "  dew  point,''  there  is  precipitation. 


246  NEW  PHYSICAL   GEOGRAPHY. 

170.  Dew  and  Frost.  —  (A)  Dew.  —  At  night  the  lowe\ 
air  is  chilled  by  contact  with  the  ground,  which  is  cooled  by 
radiation.  If  the  air  is  damp,  some  of  the  vapor  is  then  con- 
densed as  dew  ;  and  if  it  is  veri/  humid,  dew  may  begin  to 
form  even  before  sunset.  The  formation  of  dew  is  checked 
(1)  when  the  air  is  quite  dry,  (2)  when  winds  stir  the  air 
and  keep  it  from  reaching  the  dew  point,  or  (3)  when  radiar 
tion  is  interfered  with  by  clouds. 

One  reason  why  dew  forms  so  readily  on  grass  is  that  vege- 
tation is  a  good  radiator  and  hence  cools  quickly.  Another  rea- 
son is  that  there  is  water  rising  from  the  plants,  as  there  is  also, 
to  less  extent,  from  the  ground.  During  the  day  this  water  dis- 
appears by  evaporation  and  is,  therefore,  unnoticed  ;  but  at  night, 
when  the  air  is  saturated,  evaporation  is  so  checked  that  the 
water  gathers  on  the  surface  of  the  leaves  and  grass. 

Summary.  —  Dew  is  caused  (1)  by  the  chilling  of  air  to  the  dew 
point  hy  the  cool  ground,  and  (2)  by  the  rising  of  water  from  plants. 
Dry  air,  winds,  and  clouds  are  unfavorable  to  the  formation  of  dew. 

(B)  Frost.  —  Frost  is  not  frozen  dew,  but  the  solid  form 
assumed  when  vapor  condenses  at  temperatures  below  freez- 
ing. Even  when  the  general  temperature  is  above  freezing, 
frost  may  visit  some  localities.  Low,  swampy  ground  is  first 
affected  because  (1)  the  air  is  damper,  and  (2)  air  cooled  on 
the  hillsides  slides  down  to  these  low  places. 

Sometimes  frost  comes  so  early  in  the  fall  that  fruit  not  yet 
quite  ripe  is  destroyed ;  and  late  spring  frosts  often  do  great 
damage  to  buds.  Such  frosts  occur  during  nights  when  the  air  is 
so  clear  that  radiation  proceeds  readily.  Frosts  cause  the  leaves 
to  change  color,  and  finally  to  fall ;  then  for  a  time  the  trees  are 
dormant,  burstin^^  forth  into  new  life  with  the  return  of  warmth 
in  the  spring.  Many  plants  are  killed  by  the  first  frost,  leaving 
only  their  seeds,  bulbs,  or  roots  to  grow  the  next  season. 

Summary.  —  Frost  is  the  solid  form  assumed  by  condensed  vapor 
at  temperatures  below  freezing.  Frosts  first  occur  in  loiv,  damp 
places;  and  early  fall  and  late  spring  frosts  do  damage  to  plants. 


THE  ATMOSPHERE.  247 

171.  Fog  and  Clouds.  —  (A)  Fog.  — ^When  we  breath  into 
'3old  air,  the  vapor  of  the  breath  is  condensed  into  particles 
of  water  so  small  that  they  float,  forming  a  tiny  fog.  Fog  is 
formed  when  damp  air  is  chilled  in  other  ways.  For  exam- 
ple, it  often  forms  at  night  when  the  air  over  low,  damp 
land  is  chilled  to  the  dew  point ;  or  it  may  form  when  two 
currents  of  air  are  mixed,  one  cool,  the  other  damp  and  warm. 
Fogs  at  sea  are  often  caused  in  this  way. 

One  of  the  foggiest  places  in  the  world  is  on  the  path  of  trans- 
atlantic steamers  south  of  Newfoundland.  Here  the  warm  Gulf 
Stream  drift  and  the  cold  Labrador  current  are  near  together ;  and 
winds  from  one  to  the  other  cause  vapor  to  condense  into  fog  par- 
ticles. Vessels  rarely  pass  the  Banks  of  jSTewfoundland  without 
encountering  some  fog ;  and  in  it  many  a  boat  has  been  lost  by 
collision  with  another,  or  with  an  iceberg,  or  by  running  aground 
on  the  shoals.  Fog  is  one  of  the  most  dreaded  dangers  of  the 
sea,  and  cautious  captains  reduce  their  speed,  and  keep  the  fog- 
horns blowing  to  warn  other  vessels  of  their  approach.  In  har- 
bors, navigation  is  sometimes  completely  stopped  by  dense  fogs. 

Dust  particles,  by  supplying  solids  on  which  the  water  may  col- 
lect, aid  in  the  formation  of  fog.  It  is  believed  that  the  fogginess 
of  London  is  partly  due  to  the  large  amount  of  dust  in  the  neigh- 
borhood of  that  great  city.  The  fog  of  London  is  sometimes  so 
dense  that  it  is  necessary  to  stop  all  traffic  on  the  streets,  and  even 
to  close  the  stores. 

Summary.  — Fog  is  caused  by  the  chilling  of  air  to  the  dew  point, 
forcing  some  of  the  vapor  to  condense  to  tiny  drops.  Dust  particles 
supply  solids  for  the  icater  to  condense  on. 

(B)  Clouds.  —  Clouds  are  also  made  by  the  condensation 
of  vapor.  Most  clouds  are  fog  or  mist,  though  the  highei 
ones,  where  the  temperature  is  below  freezing,  are  composed 
of  snow  or  ice  particles.  Many  clouds,  especially  on  sum- 
mer days,  are  caused  by  the  rising  of  warm,  damp  air.  As 
the  air  rises  it  expands  and  cools  ;  and  when  the  dew  point  is 
reached,  fog  particles  grow,  forming  clouds.     Clouds  are  also 


'Ji'iTS  NEW  PHYSICAL   GEOGRAPHY. 

ca.iised  when  damp  air  blows  agaiust  a  cold  surface,  for  ex- 
Jtinple,  a  mountain  slope  (Fig.  400).  Still  another  cause  for 
clouds  is  the  contact  of  two  currents  of  air,  one  above  the 
other,  one  cold,  the  other  warmer  and  humid. 

Clouds  assume  many  weird  and  beautiful  forms  (Fig,  402). 
Those  that  overspread  the  sky,  having  the  appearance  of  layers, 
or  strata,  are  called  stratus  clouds.  They  are  common  during 
stormy  weather,  and  are  usually  low  in  tho  sky,  often  so  low  that 
they  hide  the  tops  of  the  hills.  Frequently,  especially  in  winter, 
they  cover  hundreds  of  square  miles  and  last  two  or  three  days, 
while  from  them  large  quantities  of  rain  fall. 

The  clouds  formed  by  the  rising  of  air  on  warm  summer  days 
are  called  cumulus  clouds  (Fig.  402).  A  flat  base,  usually  several 
thousand  feet  above  the  surface,  marks  the  height  at  which  the 
rising  vapor  begins  to  condense.  Extending  above  this  base, 
sometimes  to  a  height  of  a  mile,  are  a  series  of  cloud  domes  which 
are  often  very  beautiful,  especially  when  lighted  and  colored  by 
the  rays  of  the  setting  sun.  Cumulus  clouds  often  develop  into 
thunder-heads. 

A  third  common  type  is  the  cirrus  cloud  (Fig.  402),  which  is 
often  five  or  six  miles  above  the  surface.  Unlike  the  other  two 
types,  these  clouds  are  made  of  transparent  ice  particles ;  and 
they  are  so  thin  that  the  sun  shines  through  them.  It  is  in 
cirrus  clouds  that  rings  around  the  sun  and  moon  are  often 
seen  (p.  233).  The  cirrus  clouds  vary  greatly,  some  having  a 
most  delicate  and  beautiful  feathery  and  plumed  form. 

There  is  every  gradation  between  the  three  types  of  clouds. 
To  these  intermediate  forms  compound  names  are  given  as  follows: 
cirro-stratus,  strato-cirrus,  cirro-cumulus,  cumulo-cirrus,  cumulo- 
stratus,  and  strato-cumulus.     The  rain  cloud  is  called  nimbus. 

Summary.  —  Clouds  are  mode  of  fog,  mist,  snow,  and  ice  particles. 
They  are  caused  by  the  condensing  of  vapor  from  various  causes,  — 
rising  and  expandiyig,  bloici}ig  against  cold  surfaces,  and  contact 
of  cold  and  warmer,  damj?  currents.  Stratus  clouds  are  low,  and 
spread  over  large  areas  ;  cumulus  clouds  rise  in  domes  above  a  fat 
base  ;  cirrus  are  thin,  fleecy  clouds  high  in  the  air  and  are  made 
of  ice  particles.     TJiere  are  many  variations  betioeen  these  types. 


THE  ATMOSPHERE.  249 

172.  Rain,  Snow,  and  Hail.  —  (A)  Rain, — Fog  particlea 
111  clouds  may  grow  to  such  size  that  thej  can  no  longer  float. 
They  then  fall  as  raindrops.  The  growth  of  raindrops  is 
due  to  several  causes:  (1)  continued  condensation  of  vapor; 
(2)  union  of  fog  particles,  driven  together  by  currents  of  air; 
and  (3)  union  of  particles  as  they  fall  through  the  cloud. 
Thus  rain  is  merely  the  result  of  a  continuation  of  the  process 
of  cloud  formation.  If  the  vapor  condenses  rapidly,  as  in 
summer  thunder-clouds,  the  drops  may  grow  to  great  size. 

Kain  may  evaporate  on  its  way  from  the  clouds  ;"':i^  tail  to 
reach  the  ground.  Such  streamers  of  rain,  descending  part  way 
to  the  earth,  may  sometimes  be  seen  in  summer.  In  other  cases, 
rain  on  its  way  down  may  freeze  in  passing  through  a  cold  layer 
of  air,  forming  sleet.  Some  sleet  is  snow  that  has  partly  melted, 
and  then  frozen  before  reaching  the  ground. 

Summary.  —  Continued  condensation  of  vapor  in  cloud  formation, 
and  the  union  of  the  fog  particles,  form  raindrops  so  heavy  that  they 
must  fall  to  the  earth. 

(B)  Snow.  —  Snowflakes  are  not  frozen  raindrops,  but  are 
formed  when  vapor  is  condensing  in  a  cloud  at  temperatures 
below  freezing 
point.  If  the  snow- 
flake  grows  without 
interference,  it  is  a 
regular  and  beauti- 
ful crystal  (Fig. 
403).     It  grows  as 

regularly  as  salt  or 

1  1.  ^       '  Fig.  403.  —  Snow  crystals, 

alum    crystals   in   a  '' 

solution  that  is  slowly  evaporating.     The  feathery  frost  on 

window  panes  is  also  caused  by  crystal  growth,  when  vapor 

condenses  at  temperatures  below  the  freezing  point. 

There  are  several  reasons  why  snowflakes  are  usually  irregular: 
(1)  the  crystals  are  often  broken;  (2)  several  are  often  united. 


250 


NEW  PHYSICAL   GEOGRAPHY, 


forming  a  matted  mass ;  (3)  as  the  snow  falls  it  is  sometimes 
partly  melted  in  passing  through  a  warmer  layer  of  air.  In 
many  cases  snow  melts  entirely,  reaching  the  ground  as  rain. 
This  is  often  illustrated  in  hilly  countries,  when  hilltops  are 
covered  with  snow  while  100  or  200  feet  lower,  in  the  valleys, 
rain  is  falling. 

Summary.  —  Snoivflakes  are  crystals,  built  up  by  the  condensing 
of  vapor  at  temperatures  below  freezing.  They  are  often  broken, 
matted,  or  partly  melted  on  the  ivay  down,  becoming  irregular. 

(C)  Hail.  — Hail  is  formed  in  violent  storms,  such  as  tor- 
nadoes and  thunder-storms,  where  there  are  strong,  whirling 

currents  of  air. 
Hailstones  are 
balls  of  ice,  built 
up  by  condensing 
vapor  as  they  are 
whirled  up  and 
down  in  the  vio- 
lent currents, 
freezing,  melting, 
and  freezing  again 
as  they  pass  from 
warm  to  cold  cur- 
rents. For  this  reason  they  are  often  made  of  several  layers, 
or  shells,  of  ice.  They  may  grow  to  great  size,  and  may  be 
kept  suspended  by  the  rising  currents  long  after  they  are 
heavy  enough  to  fall  through  quiet  air.  When  they  fall, 
usually  at  the  margin  of  a  storm,  they  often  break  window 
glass  and  do  great  damage  to  crops.  Conditions  favoring 
the  formation  of  large  hailstones  are  fortunately  not  common^ 
and  their  effects  are  confined  to  very  limited  areas. 

Summary.  —  Hailstones  are  made  of  ice,  formed  by  condensing 
vapor  in  whirling  air  currents.  They  may  grow  to  large  size  befot^. 
they  fall,  then  often  doing  considerable  damage. 


Fig.  404.  —  Hailstones.    Compare  with  the  inches  ou 

the  ruler. 


THE  ATMOSPHERE,    ■  251 


Topical  Outline,  Questions,  and  SuGGEanoNS. 

Topical  Outline. — 162.  Composition  of  the  Ai/.  —  (A)  Oxygen 
Nitrogen,  and  Carbon  Dioxide:  percentage  of  each  ;  ar|,';on;  importance  of 
oxygen  ;  of  nitrogen  ;  of  carbou  dioxide  ;  slow  combustion  in  animals ; 
rapid  combustion ;  production  of  heat.  (B)  Water  Vapor  :  source;  evapo- 
ration; variation  in  amount ;  condensation.  (C)  Dust  Particles :  nature 
of  materials :  distribution  ;  effect  on  condensation  ;  microbes. 

163.  Effect  of  Gravity.  —  Cause  of  weight ;  amount  at  sea  level ;  reason 
for  not  noticing  pressure  ;  density  of  lower  air  ;  rarefied  air;  effect;  effect 
of  temperature  on  density  of  air;  movements  started  by  gravity. 

164.  Light.  —  Nature   of   light;    speed   of   passage;    combination    ot 
waves ;  effect  of  prism  ;  refraction ;    colors  of  spectrum ;    reflection ;  in 
stances;    mirage;    rainbow;   halos;    color  of  objects;    diffraction;    blue 
color  of  sky ;  sunset  colors. 

165.  Heat. —  (A)  Radiant  Energy:  heat  from  a  stove;  light  from  a 
stove;  radiant  energy ;  radiation;  radiant  energy  from  bodies  in  space; 
effect  of  radiation  on  stove;  on  sun;  part  reaching  earth.  (B)  Passage 
of  Radiant  Energy  :  diathermanous  ;  effect  of  air  on  heat;  effect  of  dust. 
(C)  Radiation  from  the  Earth:  earth  as  a  radiator ;  cause  of  cool  nights; 
of  cold  winter;  difference  between  land  and  water;  difference  in  frost. 
(U)  Reflection  and  Absorption:  water;  quarries;  black  objects;  white 
objects.  (E)  Conduction:  in  a  stove;  air,  water,  and  ground  as  con- 
ductors; depth  of  conduction  in  the  ground.  (F)  Convection:  in  water; 
in  air,  —  near  a  lamp,  near  a  fire,  by  heat  from  sun. 

166.  Warming  of  Land,  Water,  and  Air. —  (A)  The  Lands:  warming; 
.^^ss  of  heat ;  day  and  ni^ht ;  tropical  zone  ;  temperate  zone ;  frigid  zone ; 
lolor  of  surface;  vegetation;  exposure.  (B)  The  Waters:  comparison 
with  land  ;  heat  of  vaporization  ;  equable  climate.  (C)  The  Air:  causes 
for  warming;  causes  for  cooling;  interference  with  radiation. 

167.  Causes  for  Differences  in  Temperature  on  the  Earth.  —  (A)  Position 
of  Sun :  differences  in  height ;  reasons  why  sun  low  in  heavens  is  less 
powerful;  results.  (B)  Altitude:  decrease  in  temperature;  explana- 
tion; illustration  of  effect  of  expansion;  sunny,  spots ;  effect  of  radia- 
tion.    (C)    Other  Reasons  for  Differences :  rock;  exposure;  water;  wind. 

168.  Daily  and  Seasonal  Temperature  Changes. —  (A)  Dady  Range: 
warmest  period ;  coolest  period ;  reasons  ;  interference  with  normal  range  ; 
difference  in  amount  of  range.  (B)  Seasonal  Range :  resemblance  to  daily 
range ;  coldest  period ;  wannest  period ;  reasons ;  causes  for  differences 
in  curve. 

169.  Humidity.  —  Source  ;  distribution  ;  absolute  humidity ;  saturated 
air ;  relative  humidity ;  measuring  relative  humidity ;  effect  of  low  humid- 


252  NEW  PHYSICAL    GEOGEAPHY. 

iLy ;  of  high  humidity ;  influence  of  temperature  on  humidity ;  cause  ot 
deserts;  precipitation  ;  illustrations  of  effect  of  cooling;  dew  point. 

170.  Dew  and  Frost.  —  (A)  Dew :  cause  ;  unfavorable  conditions  ;  rea- 
son for  dew  on  grass.  (B)  Frost :  cause  ;  most  favorable  places ;  early 
md  late  frosts ;  effect  of  frost  on  plants. 

171.  Fog  and  Clouds.  —  (A)  Fog:  the  breath;  chilling  of  air;  fog  off 
Newfoundland;  dangers  to  navigation;  aid  of  dust  particles;  'London 
fog.  (B)  Clouds :  materials  ;  causes  ;  stratus ;  cumulus  ;  cirrus  ;  inter- 
mediate forms;  nimbus. 

172.  Rain,  Snow,  and  Hail. —  (A)  Rain:  reason  for  falling  ;  causes  for 
drops ;  large  drops ;  failure  to  reach  earth  ;  sleet.  (B)  Snotv :  cause ; 
snowflakes ;  frost  on  windows ;  irregularity  of  snowflakes ;  melting  of 
falling  snow.    (C)  Hail:  formation;  reason  for  shells  of  ice ;  size;  effects. 

Questions.  — 162.  (A)  What  elements  make  up  the  bulk  of  the 
air?  What  is  the  importance  of  each?  (B)  What  is  evaporation  ?  What 
difference  is  there  in  the  amount  of  vapor  in  air?  What  results  when  it 
is  condensed?  (C)  What  are  dust  particles?  Where  are  they  most 
common?    What  are  their  effects? 

163.  Has  air  weight  ?  Why  ?  How  much  ?  Why  does  not  the  weight 
of  the  air  affect  us?     In  what  two  ways  does  the  density  vary? 

.164.  What  is  light?  What  is  refraction ?  What  is  reflection  ?  What 
^.henomena  are  produced  by  reflection  and  refraction  of  light  in  its  pas- 
sage through  the  atmosphere?  What  is  the  cause  of  color  in  flowers? 
What  is  the  cause  of  the  blue  color  of  the  sky?     Of  sunset  colors? 

165.  (A)  What  is  radiant  energy?  What  is  radiation  ?  What  effect 
is  radiation  having  on  the  sun?  (B)  AVhat  are  diathermanous  bodies? 
Give  examples.  Why  does  the  sun  lose  power  in  late  afternoon  ?  (C) 
Why  does  the  ground  become  cool  at  night  and  cold  In  winter?  What 
difference  is  there  in  the  radiation  from  bodies?  (D)  Give  ilhistrations 
of  reflection.  Give  illustrations  of  absorption.  (E)  What  is  conduction  ? 
What  effect  has  it  on  earth,  air,  and  water  ?  (F)  What  causes  convection 
in  water?     Give  illustrations  of  convection  of  air. 

166.  (A)  Why  is  not  the  ground  excessively  warmed?  What  differ- 
ences are  there  in  the  three  zones?  What  other  causes  for  difference  are 
there?  (B)  State  the  reasons  why  water  warms  more  slowly  than  land. 
What  is  heat  of  vaporization?  Compare  land  and  w^ter  in  winter  and 
at  night.  What  is  an  equable  climate?  (C)  How  is  the  air  warmed? 
How  is  it  cooled ?     Why  is  muggy  air  oppressive? 

167.  (A)  Why  is  the  sun  less  powerful  when  low  than  when  high? 
State  three  important  effects  of  differences  in  sun's  position.  (B)  Why 
are  highlands  cool?  Are  any  parts  warm?  What  is  the  effect  of  radia- 
tion V     (C)   What  other  reasons  are  there  for  differences  in  temperature  V 


THE  ATMOSPHERE,  253 

168.  (A)  When  are  the  warmest  and  coolest  times  of  day?  Why? 
What  causes  are  there  for  interference  with  the  normal  daily  range? 
For  differences  in  the  amount  of  daily  jange  ?  (B)  When  are  the  warmest 
and  coolest  times  of  the  year?  Why?  What  reasons  are  there  for  differ- 
ences in  the  normal  seasonal  curve? 

169.  AYhat  is  absolute  humidity?  WLat  is  saturated  air?  What  is 
relative  humidity  ?  What  is  the  result  of  raising  the  temperature  ?  What 
is  the  cause  of  some  deserts?  What  is  the  result  of  lowering  the  tem- 
perature?    What  causes  precipitation?     Illustrate.     What  is  dew  point? 

170.  (A)  What  is  the  cause  of  dew?  Under  what  conditions  is  there 
no  dew?  Why  is  there  so  much  dew  on  grass?  (B)  What  is  frost? 
Why  does  frost  first  visit  low,  damp  places  ?     What  are  its  effects? 

171.  (A)  What  are  the  causes  for  fog?  What  are  the  conditions  on 
the  Banks  of  Newfoundland?  Why?  What  is  the  effect  on  navigation ? 
What  relation  have  dust  particles  to  fog  ?  (B)  Of  what  are  clouds  made  ? 
How  are  they  caused  ?     Name  and  describe  each  of  the  cloud  types. 

172.  (A)  AVhat  is  the  cause  of  rain  ?  Why  do  the  drops  vary  in  size  ? 
What  is  sleet?  (B)  What  are  snowflakes?  How  formed?  Why  are 
they  often  irregular?  (C)  What  is  the  cause  of  hailstones?  Why  do 
they  sometimes  grow  so  large  ? 

Suggestions. —  (1)  Recall  Experiments  1,  2,  3,  4,  and  6  of  Chapter 
II,  p.  30.  (2)  Let  a  beam  of  sunlight  enter  a  darkened  room  and  notice 
the  dust  that  it  lights.  Watch  the  sky  to  see  if  it  is  sometimes  hazy. 
Is  it  clearer  after  a  rain  ?  Why  ?  (3)  By  means  of  an  air  pump  show 
that  air  has  pressure.  The  teacher  of  physics  can  tell  how  this  is  to  be 
done.  (4)  Obtain  a  prism  of  glass  from  the  physical  laboratory  and  allow 
a  ray  of  sunlight  to  pass  through  it  in  order  to  study  the  prismatic  colors. 
(5)  Place  a  stick  in  water  and  notice  that  it  appears  to  bend  below  the 
water.  This  is  due  to  refraction.  (6)  Heat  a  brick  or  a  stone  and  suspend 
it  by  a  wire.  Why  does  it  become  cool  ?  Does  the  thermometer  show 
rise  of  temperature  when  placed  near  it?  Why  ?  (7)  Try  the  experiment 
with  black  and  white  cloth,  mentioned  on  p.  236,  using  ice  instead  of  snow. 

(8)  Place  a  thermometer  in  the  shade  in  such  a  position  that  sunlight 
can  be  reflected  on  it  by  means  of  a  mirror.     Does  the  temperature  rise? 

(9)  Place  one  end  of  a  bar  of  iron  in  the  fire.  Does  the  other  end  become 
warm  ?  Why  ?  Place  an  equal  bulk  of  several  substances  —  for  example, 
iron,  soil,  and  rock  —  on  the  stove  for  a  short  period  to  test  which  first  be- 
comes warm  by  conduction.  Use  a  thermometer  to  determine  this.  It  can 
also  be  told  by  putting  a  thin  layer  of  paraffin  on  each,  noticing  on  which 
it  first  begins  to  melt.  (10)  Study  convection  in  water,  using  a  glass  dish 
with  muddy  water  so  as  to  see  its  movement.  Study  the  convection  of 
air  near  a  lamp,  clouding  the  air  with  smoke  (this  can  be  obtained  W 


254  NEW  PHYSICAL   GEOGRAPHY, 

/ighting  a  piece  of  cloth)  so  that  its  movement  may  be  seen.  Explain  the 
principle  of  a  lamp;  of  a  fireplace.  How  is  your  schoolhouse  ventilated? 
Does  the  fresh  air  come  in  above  or  below?  Why?  (11)  Place  a  brick 
and  a  pan  of  water  (as  deep  as  the  thickness  of  the  brick)  on  a  hot  stove 
or  over  a  Bun  sen  burner.  Carefully  weigh  each  before  placing  them  there. 
When  the  brick  has  become  warm,  take  the  temperature  of  each  at  the 
top.  At  the  bottom.  Why  is  one  the  same  temperature  throughout-, 
the  other  hot  at  the  bottom  and  only  warm  at  the  top  ?  Which  shows  the 
higher  temperature?  Why?  When  cool,  weigh  them  again.  Has  either 
lost  weight?  Why?  (12)  Do  the  same  with  water  and  soil,  leaving  a 
thermometer  in  each  and  recording  the  changes.  In  which  does  the  tem- 
perature rise  faster  ?  Which  cools  faster?  (13)  Take  the  temperature 
at  6,  8,  10,  12,  2,  4,  G,  8,  and  10  o'clock  for  one  day.  Construct  a  curve 
similar  to  Fig.  395.  Keep  records  for  a  week,  and  construct  curves  to  see 
if  they  are  all  alike.  (14)  A  seasonal  curve  can  also  be  made,  getting  the 
data  from  the  Annual  Repo-rt  of  the  United  States  Weather  Bureau,  in 
wdiich  daily  averages  are  given  for  many  places.  (15)  With  a  bicycle 
pump  illustrate  the  warming  of  air  by  com.pression,  and  cooling  by  ex- 
pansion (p.  241).  A  little  fog  can  be  produced  by  j)lacing  a  dish  of  hot 
water  where  the  escaping  cool  air  passes  over  it.  (16)  Make  observa- 
tions on  condensation,  —  blowing  on  a  cold  window,  for  example.  In 
warm,  damp  air,  watch  drops  collect  on  a  glass  of  ice  water.  That  the 
water  does  not  come  from  within  the  glass  may  be  proved  by  placing  a 
glass,  without  water,  on  ice  until  it  is  cold,  then  putting  it  in  the  room. 
The  same  thing  may  also  be  shown  by  putting  salt  and  ice  in  a  bright  tin 
dipper.  The  temperature  of  dew  point  can  be  determined  by  putting  a 
thermometer  in  the  salt  and  ice,  reading  the  temperature  at  the  moment 
water  begins  to  cloud  the  surface  of  the  dipper.  (17)  Study  frost :  the 
time  of  its  coming;  the  places  where  it  comes  first;  and  any  other  facts 
you  can  find  out  by  observation.  (18)  For  a  few  days  observe  the  clouds 
carefully,  classifying  those  you  see. 

Reference  Books.  —  Davis,  Elementary  Meteorology/,  Ginn  &  Co.,  Bos- 
ton, 1894,  §2.70;  Ward,  Practical  Exercises  in  Elemeiilarij  Meteorology, 
Ginn  &  Co.,  Boston,  1896,  $1.12;  Waldo,  Modern  Meteorology,  Scrib- 
ner's  Sons,  New  York,  1893,  $1.50;  Elementary  Meteorology,  American 
Book  Co.,  New  York,  1896,  $1.50 ;  Russell,  Meteorology,  Macmillan  & 
Co.,  New  York,  1894,  $4.00;  Tyndat  l.  The  Forms  of  Water,  Appleton  & 
Co.,  New  York,  1872,  $1.50;  Illustratice  Cloud  Forms,  U.  S.  Hydrographic 
Office,  Washington,  1897,  $1.00;  Annual  Reports  and  Monthly  Weather 
Reviews,  U.  S.  Weather  Bureau,  Washington  ;  Bartholomew,  Physical 
Atlas,  Vol.  Ill,  Meteorology,  Archibald  Constable,  London,  1899,  $13.00. 


CHAPTER    XIII. 

V7INDS   AND    STORMS. 

WINDS. 

173.  Relation  between  Winds  and  Air  Pressure.  —  Winds 
are  tlie  result  of  differences  in  the  air  pressure,  or  weight. 
It  is  easier  to  understand  their  cause  if  we  consider  the 
atmosphere  to  be  composed  of  a  great  number  of  air  columns 
which  gravity  holds  to  the  earth.  If  the  sun's  heat  warms 
the  air  in  one  place,  the  columns  at  that  place  become  lighter 
than  in  places  not  so  warmed  (p.  231).  Light  air  is  said  to 
have  a  low  pressure^  heavy  air  a  high  pressure^  because  tho 
heavier  the  air,  the  higher  it  pushes  the  mercury  up  in  the 
tube  of  the  barometer  (Appendix  G).  The  air  moves,  or 
flows,  from  places  of  high  toward  places  of  low  pressure,  thus 
causing  winds.  On  a  larger  scale,  it  is  much  the  same  as 
the  movement  of  the  cooler  and  heavier  air  which  crowds  up 
the  warm,  lighter  air  in  a  lamp  (p.  236). 

The  difference  in  air  pressm^e  which  causes  winds  is  often 
known  as  the  barometric  gradient.  It  is  so  named  because  the 
air  flows  from  a  region  of  high  pressure,  or  high  barometer,  to  one 
of  low,  as  if  it  were  going  down  a  grade,  or  gradient,  as  flowing 
water  does.  It  is  not  to  be  understood,  of  course,  that  there  is  a 
real  slope  or  grade,  but  merely  lighter  air  in  one  place  than  in 
another.  If  the  difference  in  pressure  is  great,  the  barometric 
gradient  is  so  high  that  the  air  moves  swiftly,  as  water  flows 
down  a  steep  grade. 

Summary.  —  Winds  are  due  to  a  Jlotving  of  air  from  regions  of 
heavy  air,  or  high  pressure,  to  regions  of  low  presswe  ;  and  the 
difference  in  pressure  is  known  as  the  barometric  gradient. 

256 


256  NEW  PHYSICAL   GEOGRAPHY, 

174.  Sea  and  Land  Breezes.  —  A  simple  illustration  of 
winds  is  often  found  along  ocean  and  lake  shores  on  hot 
days.  On  such  days  the  land,  and  the  air  over  it,  become 
much  warmer  than  the  water  (p.  288).  Soon  the  heavier  air 
from  the  water  flows  in  as  a  cool,  refreshing  sea  breeze,  push- 
ing upward  the  warm,  lighter  air  that  rests  on  the  land. 

When  the  sea  breeze  begins  to  blow,  the  temperature,  which 
may  have  risen  to  80°  or  90°,  commences  to  fall,  and  the  rest  of 
the  day  is  pleasantl}^  cool.  It  is  partly  because  of  the  cool  sea 
breezes  that  so  many  people  go  to  the  seashore  to  spend  their 
summer  vacations.  Along  tropical  coasts,  sea  breezes  are  very 
pronounced  and  of  almost  daily  occurrence. 

At  night  a  land  breeze  often  blows  out  over  the  water.  The 
reason  for  this  is  that  the  land  cools  by  radiation  faster  than  the 
water  (p.  238),  and  the  cool  land  air  slides  out  over  the  sea,  push- 
ing up  the  warmer  air  that  rests  there.  Sailboats,  becalmed  off 
shore  when  the  sea  breeze  dies  down,  are  able  to  reach  port  late  in 
the  evening  when  the  land  breeze  begins  to  blow. 

Summary.  —  Sea  breezes  are  caused  by  cool  air  from  the  seafloiv- 
ing  in  on  hot  days  and  pushing  up  the  ivarm,  light  air  over  the  land. 
At  night,  land  breezes  bloic  out  over  the  sea  from  the  cooler  land. 

175.  Mountain  Valley  Breezes.  —  AYinds  similar  to  the  land 
breezes  are  noticed  at  night  in  hilly  and  mountainous  regions. 
As  the  land  cools  by  radiation,  the  cool,  heavy  air  slides  down 
the  slopes,  causing  winds  that  often  gain  great  force  late  at  night. 
During  the  day,  as  the  valley  sides  are  warmed,  the  air  moves  up 
the  valleys  ;  but  this  movement  does  not  cause  winds  so  strong 
as  those  at  night,  when  the  air  is  flowing  down  grade  and  gather- 
ing from  many  tributary  valleys  into  one  main  valley. 

Summary.  —  At  night,  cool  air  slides  down  valleys,  forming  wirids ; 
and  air  passing  up  the  valleys  during  the  day  causes  lighter  breezes. 

176.  Monsoon  Winds.  —  On  some  of  the  continents,  there 
are  changes  in  wind  direction  from  summer  to  winter. 
These  seasonal  winds,  know»  as  monsoons,  are  best  devel- 
oped in  Asia  Cp-  259)r 


WINDS   AND   STOBMS^ 


•J57 


In  summer  the  land  becomes  warmer  than  the  watei^  t^iul 
air,  therefore,  blows  from  the  Pacific  and  Indian  oceans  toward 
the  warm  interior,  forming  the  summer  monsoon.  In  winter, 
when  radiation  cools  the  Asiatic  highlands,  the    heavy  air 


Fig.  405.  — The  summer  (left  hand)  and  winter  (right  hand)  monsoons  of  India. 

moves  outward  toward  the  warmer  oceans,  forming  the 
winter  monsoons.  Thus  twice  each  year  the  winds  change. 
In  India  the  changes  are  so  regular,  and  the  winds  so  steady, 
that  in  early  times  sailing  vessels  went  there  in  summer  and 
left  in  winter,  in  order  to  have  fair  winds  both  ways. 

All  continents  show  some  tendency  toward  the  develoiDment  of 
monsoon  winds;  but  in  most  cases  other  winds  are  too  well  estab- 
lished for  the  monsoons  to  develop  perfectly.  For  example,  the 
regular  winds  of  northeastern  United  States  are  from  the  west ; 
but  they  are  much  steadier  in  winter  than  in  summer  (Figs.  409, 
410).  The  reason  for  this  is  that  in  winter  the  outflow  of  cold  air 
from  the  land  strengthens  the  west  winds,  while  in  summer  the 
Inflow  of  cool  air  from  the  ocean  weakens  them  ;  but  the  summer 
inflow  is  not  strong  enouf?h  to  completely  destroy  the  west  wind 
movement  and  form  regular  monsoons. 

Summary.  —  Monsoon  winds,  best  developed  in  Asia,  are  due  to 
the  inflow  of  air  from  the  ocean  to  the  ivarmer  land  in  summer,  and 
the  outflow  of  air  from  the  cold  land  in  ivinter. 


258  NEW  PHYSICAL    GEOGRAPHY, 

177.  Wind  Systems  of  the  Earth.  —  Even  greater  air  move- 
ments than  those  just  described  are  caused  by  differences  in 
temperature  between  the  warm  tropical  belt  and  the  cooler 
zones  north  and  south  of  it.     Tlie  winds  thus  started  affect 

all  zones,  all  continents, 


CALMS 


H.POLE-^-^  * S.POLE 


and  all  oceans. 

(A)  Comparison  luith  a 
Stove.  —  In  certain  re- 
spects this  great  circula- 
tion may  be  compared  to 
the  movements  of  air  in  a 
room  heated  by  a  stove. 

'^Tft.  406.  — A  diagram  to  illustrate  the  air       The  air  arOUnd   the  stove 
circulation  of  the  earth.    E  is  equator.  -^  ^^^.^^^d,  and  the  COOler, 

heavier  air  in  other  parts  of  the  room  crowds  in  and  pushes 
the  warm  air  upward.  There  is,  therefore,  (1)  a  movement 
toward  the  stove  ;  (2)  a  rising  above  it ;  (3)  an  upper  cur- 
rent away  from  it ;  and  (4)  a  settling  at  a  distance  from  it. 
because  of  the  heated  belt  of  the  tropical  zone  there  are 
similar  movements  on  the  earth  (Fig.  406).  These  are  (1)  a 
movement  of  air  along  the  surface  toward  the  equator  ;  (2)  a 
rising  in  the  torrid  zone  ;  (3)  an  upward  movement  away 
from  this  zone ;  and  (4)  a  settling  north  and  south  of  it. 

Summary.  —  Both  in  a  room  heated  by  a  stove,  and  on  the  earth, 
warmed  in  the  torrid  zone,  there  is  a  movement  of  air  toward  the 
warm  place,  a  rising,  an  outjlow  above,  and  a  settling. 

(B)  Effect  of  notation.  —  While  air  currents  in  a  room 
move  straight  toward  the  stove,  the  winds  of  tlie  earth  are 
gradually  turned  from  a  straight  course  by  the  influence  of 
the  earth's  rotation.  Currents  of  air,  like  water  (p.  191), 
are  turned,  or  deflected,  in  the  northern  hemispliere  toward 
the  right,  in  the  southern  tow^ard  the  left.  This  effect  of 
rotation  is  therefore  called  right-hand  deflection  in  the  north- 
ern hemisphere,  and  left-hand  deflection  in  the  southern. 


}lGi)::}niO::}\ 


THS:yEAR- 


i'lG.  407.  —  Isobars  (lines  of  equal  pressure)  for  the  world.  The  dark  shadmg 
represents  lii^h  pressure.  The  figures  (29.85  for  example)  are  inches  to 
which  the  mercury  in  a  barometer  rises,  being  highest  where  the  air  pressure 
is  greatest.  In  the  dark  zones  of  high  pressure,  the  horse  latitude  belt,  air  is 
settling;  it  moves  thence  toward  the  low  pressure  belt  of  the  warm  torrid 
zone,  forming  the  trade  M-inds,  and  toward  the  low  pressure  areas  near  the 
poles,  forming  the  prevailing  westerlies. 


Fig.  408.  —  A  sketch  map  showing  the  prevailing  winds  and  wind  belts  of  the 

earth  in  winter. 


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WINDS  ANJJ   STOEMS.  259 

Summary.  —  The  effect  of  the  earth^s  rotation  turns  luinds  toivard 
ihe  right  {right-hand  deflection)  in  the  iiorthern  hemisphere,  and 
toward  the  left  (left-hand  deflection')  in  the  southern. 

(C)  Belt  of  Calms. — In  the  torrid  zone,  where  the  air  is 
rising,  there  is  little  wind,  because  the  air  movement  is 
vertical  (Fig.  406)  instead  of  horizontal.  This  is  a  region 
of  baffling  calms,  sometimes  called  the  doldrums^  sometimes 
the  belt  of  calms  (Figs.  408-410).  This  belt  does  not  remain 
stationary,  but,  as  the  belt  of  greatest  heat  changes  position 
with  the  season  (Figs.  439,  440),  migrates  northward  and 
southward. 

Summary.  —  Where  the  air  is  rising,  in  the  torrid  zone,  there  is  a 
region  of  calms  ivhich  changes  position  with  the  season. 

(D)  Trade  Winds. — The  air  currents  that  move  toward 
the  belt  of  calms,  known  as  the  trade  winds  (Figs.  406,  408- 
ilO),  blow  with  great  steadiness,  especially  over  the  ocean, 
[ndeed,  islands  in  the  trade-wind  belts  commonly  have  steep, 
wave-cut  cliffs  on  the  windward  side,  against  which  the  surf 
ils  ever  beating.  Instead  of  blowing  directly  from  the  north 
in  the  northern  hemisphere,  and  from  the  south  in  the  south- 
ern, the  trades  are  deflected  by  the  influence  of  rotation, 
becoming  northeast  winds  in  the  northern  hemisphere  and 
southeast  in  the  southern.  These  are,  therefore,  called  the 
northeast  trades  and  southeast  trades  respectively. 

As  the  belt  of  calms  migrates  northward  and  southward 
each  season,  the  trade  winds  also  change  position,  being 
farther  north  in  summer  than  in  winter.  F^or  this  reason, 
places  near  the  border  of  the  trade-wind  and  calm  belts  have 
alternate  seasons  of  calms  and  trade  winds  (Figs.  439,  440). 

The  reason  why  the  monsoons  are  best  developed  in  Asia 
(p.  256)  is  the  nearness  of  the  belt  of  calms.  The  winter  out- 
flow of  cold  air  strengthens  the  northeast  trades  ;  but  in  summer, 
when  the  belt  of  calms  has  migrated  northward  to  the  laud,  the 
southeast  trades  extend  across  the  equator  to  the  land.     That  i& 


260 


NEW  PHYSICAL   GEOGRAPHY. 


in  summer  the  land  is  so  warm  that,  in  this  region,  the  southeast 
trades  are  strengthened  and  the  northeast  trades  destroyed. 

Summary.  —  The  steady  movement  of  air  toward  the  torrid  zone 
forms  the  trade  ivinds,  which,  deflected  by  rotation,  blow  from  the 
northeast  in  the  northern  hemisphere  and  the  southeast  in  the  south- 
ern.    These  belts  migrate  northward  in  summer,  southward  in  winter, 

(E)  Antitrades. — The  air  that  rises  in  the  belt  of  calms 
flows  northward  and  southward,  high  above  the  earth  (Fig. 
406).  Turned  by  the  influence  of  rotation,  these  upper  cur- 
rents, or  antitrades^  move  from  the  southwest  in  the  northern 
hemisphere  and  from  the  northwest  in  the  southern  hemi- 
sphere ;  that  is,  opposite  in  direction  to  the  lower  trade  winds. 
The  movement  of  higher  clouds,  and  of  ash  erupted  from  vol- 
canoes, proves  this.  On  high  peaks  which  rise  above  the  trade 
winds,  as  in  the  Hawaiian  Islands,  the  antitrades  may  be  felt. 

Summary.  —  The  outflow  of  air  that  rises  in  the  belt  of  calms  is 
known  as  the  antitrades,  ivhich  blow  above  the  trades. 

(F)  Prevailing  Westerlies. 
■ —  On  its  ^vay  toward  the 
poles  some  of  the  upper  air 
settles  to  the  surface,  but 
much  continues  on  to  high 
latitudes.  There  is,  there- 
fore, a  movement  of  air  from 
a  broad  belt  in  the  torrid  zone 
toward  the  small  area  around 
each  pole.  It  niay  be  com- 
pared to  the  movement  of 
water  toward  the  small  outlet 
of  a  wash  basin.  In  its 
attempt  to  reach  tliis  outlet 
the  water  commences  to  whirl 
about  it  ;  and,  in  a  similar  way,  the  air  forms  a  whirl  about 
each  pole  known  as  the  circumpolar  whirl  (Fig.  411). 


Fig, 


,  411.  —  Ideal  circulation  of  air 
near  the  surface  in  the  southern 
hemisphere.  Trade  =  trade-wind 
belt.  //,  H=  horse  latitudes. 
G.  W.  =  circumpolar  whirl. 


WINDS  AND  STOMMS.  261 

The  direction  that  this  whirl  of  air  takes  is  determined  by 
the  influence  of  rotation  ;  that  is,  the  air  currents  are  turned 
toward  the  right  in  the  northern  hemisphere  and  toward  the 
left  in  the  southern.  This  causes  winds  from  a  westerly  direc- 
tion in  each  hemisphere.  Therefore  these  wind  belts  are  called 
the  prevailing  westerlies  (Figs.  406,  408—411).  They  cover  the 
greater  part  of  the  two  temperate  and  the  two  frigid  zones. 

These  winds,  as  well  as  the  others,  are  interfered  with  by  various 
causes.  For  example,  they  are  often  strongest  during  the  daV;  be- 
cause of  differences  in  pressure,  caused  by  the  warmth  of  the  sun. 
When  the  sun  sets  the  wind  often  dies  down.  Storms,  sea  breezes, 
and  the  effects  of  topograpliy,  such  as  the  influence  of  valleys,  also 
interfere  with  the  force  and  direction  of  the  winds. 

Winds  are  commonly  less  steady  and  strong  on  land  than  or. 
water.  The  reason  for  this  is  that  the  roughness  of  the  land,  and 
its  differences  in  temperature,  interfere  with  their  movement 
Since  in  the  southern  hemisphere  there  is  so  little  land  to  inter- 
fere with  the  regular  winds,  the  prevailing  westerlies  are  better 
developed  there  than  in  the  northern  hemisphere  (Figs.  408-411). 
Indeed,  in  the  great  Southern  Ocean,  a  vessel  can  sail  eastward 
around  the  earth  with  prevailing  fair  winds. 

There  is  so  much  land  in  the  northern  hemisphere  that  the 
westerlies  are  greatly  interfered  with ;  but  high  in  the  air,  above 
the  influence  of  the  surface,  they  blow  with  great  strength  and 
steadiness.  Any  one  can  prove  this  for  himself  by  watching  the 
upper  clouds  and  noticing  how  uniformly  they  move  eastward, 
even  when  the  wind  at  the  surface  is  from  the  opposite  direction. 

Summary.  —  Some  of  the  air  of  the  antitrades  continues  on,  form- 
ing the  circinnjjolar  ichirls.  Turned  by  the  influence  of  rotation,  these 
ivinds  blow  from  luesterly  directions  in  both  hemispheres,  forming  the 
prevailing  ivesterlies.  They  are  better  developed  over  the  Southern 
Ocea7i,  and  high  in  the  air,  than  at  the  surface  of  the  northern  hemi- 
sphere, where  they  are  interfered  tvith  by  irregulaY  land  and  by  local 
winds. 

(G)  Horse  Latitudes.  —  Between  the  trades  and  westerlies, 
in  each  hemisphere,  there  is  a  belt  known  as  thp  horse  latitudes, 


262  NE^V  PHYSKJAL    GEOGRAPHY. 

in  which  the  air  of  the  antitrades  is  steadily  settling  (  Figs.  406, 
407).  Since  the  air  movement  is  vertical,  tliis  is  a  belt  of 
relative  calm,  with  irregular,  unsteady  winds,  quite  in  contrast 
to  the  steady  trades  on  one  side  and  west  winds  on  the  other 
(Figs.  408-410).  As  the  belt  of  calms  and  the  trade-wind 
belts  migrate  northward  and  southward  witli  the  seasons 
(p.  259),  the  horse  latitude  belts  also  shift. 

Summary.  —  Tlie  horse  latitudes  are  belts  (one  in  each  hemisphere) 
of  relative  calm,  ivhere  the  air  of  the  antitrades  is  settling. 

STORMS.  1 

178.  Cyclonic  Storms.  —  (A)  Characteristics.  — The  L'nited 
States  weather  map  (Fig.  413)  shows  an  area  where  the  aii- 
pressure  is  light.  It  is,  therefore,  called  a  low  pressure  area, 
or  a  Low  (p.  255).  Around  this  center  of  low  pressure  the 
mercury  in  the  barometer  stands  higher,  and  this  fact  is  indi- 
cated by  lines  of  equal  pressure,  or  isobars.      Air  is  moving 

BROKEN  C^O^]^)S  CIRRUS  CLOUDS 

...    ^ .   ,    -i-j.-.-Si     ,<5 -.^^        ^  j^  J,  ^^  "       CLEAR 


HEAVY  STRATUS  CLaUDS  n.grr-rir<K.  ^*^^ 


DIRECTION 

OP  MOVPMENT 


Fig.  412.  —Diagram  showing  theoretical  movement  of  air  (by  arrows),  and  other 
conditions,  in  a  low  pressure  or  cyclonic  storm  area.     Describe  this  diagram. 

from  all  directions  toward  the  low  pressure  area.  Next  day 
(Fig.  414)  the  Low  has  moved  eastward  ;  but  winds  still  blow 
toward  it,  and  around  its  center  rain  falls.  This  area  of  low 
pressure  is  known  as  a  cyclonic  storm.  The  following  day  the 
storm  has  moved  still  farther  east  (Fig.  415),  and,  if  we 
should  continue  to  follow  it,  Ave  could  trace  it  out  into  the 
Atlantic,  and  possibly  even  across  northern  Europe  into  Asia. 

Summary.  —  A  cyclonic  storm  is  an  area  of  low  air  p7'essure 
toward  ivhich  ivinds  blow  from  all  directions,  and  in  which  rain  falls, 
%uch  storms  move  eastward. 

'  See  also  Appendix  II,  and  pp.  289-29.S. 


Fig.  413.  — Chart  to  show  weather  conditions,  January  7,  1893.  Isobars,  heavy 
lines ;  isotherms  dotted ;  wind's  direction  indicated  by  arrows ;  areas  of  rain 
shaded.    Compare  with  Figs.  414  and  415. 


Fm5.  414.  —  Weather  map  for  next  day,  January  8, 1893.     Path  pursued  by  storro 

center  indicated  by  chain  o'  -"Zrows 


Fig.  415.  —  Same  storm  as  Figs.  413  and  414,  showing  its  position  on  January  9, 
1893.    Trace  the  changes  for  these  three  days. 


Fig.  416.  —  Paths  followed  by  a  number  of  low  pressure  areas  during  the  month 
of  November,  1891,    The  three  in  the  ocean  are  hurricanes. 


WINDS  AND   STORMS. 


263 


(B)  Anticyclones.  —  West  of  the  cyclonic  storm  (Fig.  414) 
is  an  area  of  high  pressure  (marked  High^^  from  which  winds 


9|^.  6IRRU3  CLO0J38 


CLEAR       WE  XTH  E  R~ 


EARlftycVOiyTJY^ 


CALM  ^    g»         > 


Olfl^OTIt 
OF  MaVDIENT 


Fig.  417.  —  Diagram  showing  theoretical  circulation  (by  arrows),  and  other  con- 
ditions, in  a  high  pressure,  or  anticyclonic,  area.    Describe  this  diagram. 

blow  outward  in  all  directions,  while  the  sky  is  clear  and 
no  rain  falls.  Such  a  high  pressure  area  is  often  called  an 
anticyclone^  because  in  it  conditions  are  the  reverse  of  those 
in  cyclones.  Anticyclones  move  eastward  as  cyclonic  storms 
do,  even  crossing  the  Atlantic. 

Summary.  —  Anticyclones  are  areas  of  high  pressure  with  outward 
blowing  winds  and  clear  sky.     Tliey  also  move  eastward. 

(C)  Succession  of  Cydones  and  Anticyclones.  —  Almost 
every  weather  map 
shows  similar  areas 
of  high  and  low 
pressure  (see  Figs. 
448-453).  At  inter- 
vals of  from  three 
to  seven  days,  places 
in  northern  United 
States  are  liable  to 
be  visited,  in  fairly 
regular  succession, 
by  two  low  pressure 
areas  with  a  high 
between  (Fig.  418). 
The  passage  of  these  areas  is  readily  observed  by  watching 
the  rising  and  falling  of  the  barometer,  or  by  observing  tb.^ 


12  13 

18.92 

Fig.  418.  —  Diagram  showing"  change  of  pressure  for 
seven  successive  days  at  Ithaca,  N.Y.  Figures 
in  vertical  column  indicate  inches  and  tenths  of 
inches  of  mercury  in  the  barometer.  The  two 
drops  in  the  curve  were  caused  by  the  passage  of 
two  low  pressure  areas. 


264 


NEW  PHYSICAL   GEOGBAPHT. 


weather.  Cloudy  weather,  rain,  and  high  temperatures 
usually  accompany  the  lows,  and  clear,  cool  or  cold  weather, 
the  highs ;  while  the  wind  direction  varies  as  these  areas  pass. 

These  high  and  low  pressure  areas  follow  several  paths  (Fig. 
416).  Most  of  them  originate  either  in  the  northwest  or  south- 
west, but  some  reach  the  country  from  the  Pacific.  In  either 
case,  they  move  toward  the  east,  usually  crossing  the  Great  Lakes 
region,  going  down  the  St.  Lawrence,  and  then  out  to  sea.  The 
centers  move  500  to  1000  miles  a  day. 

Not  all  low  pressure  areas  are  true  storms,  for  those  in  which 
the  pressure  is  not  very  low  have  light  winds  and  little,  if  any, 
rain.  These  poorly  developed  low  pressure  areas  sometimes  die 
out  entirely ;  in  other  cases  they  rapidly  develop  into  vigorous 
storms.  It  is  such  irregularities  as  these  that  make  storm  predic- 
tion uncertain ;  but,  because 
they  usually  follow  regular 
courses,  most  storms  can  be 
accurately  predicted. 

Summary.  —  Cyclonic 
storms  and  anticyclones  usu- 
ally develop  in  the  7iorthivest 
or  southwest,  hut  often  come 
from  the  Pacific,  passing 
eastward  across  the  country 
in  fairly  regular  succession, 

(D)    Cause  of  Cyclonic 
Storms,  —  Cyclonic 
storms    are    great    eddies 
in  the  prevailing  wester- 
lies, and  they  occur  both 
in  the  northern  and  south- 
ern  hemispheres.       They 
may  be  compared  to  the  eddies  in  a  river  (Fig.  419),  that 
move  downstream  with  the  current  at  the  same  time  that 
water  is  whirling  from  all  directions  toward  their  centers. 


Fig.  419.  —  An  eddy  mo  vine;  downstream, 
but  with  water  whirling  toward  its 
center. 


WINDS  AND  STORMS,  265 

In  the  same  way,  while  the  storm  whirls  are  moving  east- 
ward with  the  prevailing  westerlies,  the  air  in  them  is  eddy- 
ing from  all  sides  toward  their  centers. 

Why  these  eddies  develop  is  not  certainly  known.  One  theory 
is  that  they  are  started  by  the  warming  of  air  in  some  place,  caus- 
ing it  to  be  light  and  therefore  to  rise,  as  air  rises  over  a  stove. 
Opposed  to  this  theory  is  the  fact  that  these  storms  are  most  com- 
mon and  best  developed  in  winter,  when  heat  is  least  likely  to 
cause  low  pressure  areas. 

Another  theory  is  that  the  highs  and  lows  are  air  waves  started 
in  the  westerlies.  The  regularity  with  which  they  come,  their 
strength  in  winter  when  the  west  winds  are  best  developed,  and 
other  facts,  point  to  this  as  the  more  probable  explanation.  In 
either  case,  whether  the  air  is  warmed,  or  whether  it  is  caused 
to  rise  and  fall  in  waves,  one  part  will  have  a  lower  pressure 
than  another,  and  toward  it  air  will  flow,  starting  a  whirl. 

Summary.  —  Cyclonic  storms  are  eddies  in  the  prevailing  wester- 
lies, ivith  air  wliirling  toward  their  ceyiters  from  all  sides.  Tliese 
eddies  are  low  pressure  areas,  caused  either  hy  the  ivarming  of  air 
or,  more  probably,  by  air  waves  started  in  the  westerlies. 

(E)  Influence  of  Cyclones  and  Anticyclones  on  Weather.  — • 
WINDS.  (See  also  p.  289.)  During  the  passage  of  high  and 
low  pressure  areas  the  wind  changes.  On  the  east  side  of  a 
storm  the  wind  is  from  an  easterly  quarter,  on  the  south  side 
from  the  south,  and  between  the  cyclone  and  the  anticyclone, 
from  the  west.  The  winds  do  not  move  along  straight  lines 
toward  the  center,  but  are  turned  by  the  effect  of  rotation  so 
that  they  blow  spirally  ;  and  if  the  differences  in  pressure  are 
considerable,  they  blow  with  great  force.  Near  the  center 
the  air  rises  (Fig.  412);  but  in  an  anticyclone  it  is  steadily 
settling  (Fig.  417). 

TEMPERATURE.  With  these  variations  in  wind  direction 
the  temperature  also  changes.  Air  from  the  south  is  warm, 
from  the  north,  cool  or  cold.  The  settling  air  of  the  anti- 
cyclones brings  to  the  earth  some  of  the  cool  upper  air.     Foi- 


266  NEW  PHYSICAL    GEOGRAPHY. 

these  reasons,  when  low  pressure  areas  pass  over  a  region 
there  is  usually  hot,  humid  air  in  summer,  and  damp  air 
and  rising  temperature  in  winter.  But  when  the  high  pres- 
sure areas  approach,  the  air  becomes  clear  and  cool  in  sum- 
mer, and  cold  in  winter.  Radiation  through  the  clear  air 
of  an  anticyclone  cools  the  ground  far  more  than  through 
the  humid,  cloudy  air  which  mantles  the  earth  during  the 
passage  of  a  low  pressure  area. 

RAIN.  When  air  is  settling  it  is  growing  warmer,  and, 
therefore,  its  vapor  does  not  condense.  Consequently  anti- 
cyclones cause  periods  of  dryness.  In  cyclonic  storms,  on  the 
other  hand,  the  rising  air  is  becoming  cooler,  and  its  vapor 
is  condensing,  forming  clouds  and  rain.  The  cloudy  and 
rainy  portions  of  a  well-developed  cyclonic  storm  may  covei 
an  area  with  a  diameter  of  over  1000  miles. 

There  are  two  other  important  reasons  for  rain  in  these  storms : 
(1)  those  winds  which  are  blowing  from  the  south  are  steadily 
advancing  toward  a  cooler  region ;  (2)  in  some  places  the  air  is 
forced  to  rise  over  highlands,  like  the  Appalachians  and  New 
England.  If,  in  either  case,  the  air  cools  until  it  reaches  the  dew 
point,  some  of  its  vapor  condenses. 

In  central  and  eastern  United  States  the  rain-bearing  winds  of 
cyclonic  storms  are  mainly  from  the  south  and  east.  Winds 
from  these  quarters  bear  vapor  from  the  ocean,  and  those  from 
the  south  are,  in  addition,  blowing  toward  cooler  regions.  In  New 
England,  well-developed  cyclonic  storms  are  commonly  called 
northeast  storms,  because  of  the  damp  ocean  winds  then  blowing 
from  that  quarter  toward  the  center  of  low  pressure. 

When  vapor  condenses  to  form  clouds  and  rain,  the  so-called 
''  latent  heat "  (p.  238)  is  liberated,  and  this  helps  warm  the  air. 
It  is  partly  for  this  reason  that  storms  commonly  increase  in  vio- 
lence in  passing  over  the  Great  Lakes  and  the  ocean;  for  in  these 
places  more  vapor  is  provided,  and  the  heat  from  its  condensation 
causes  lower  pressure  and,  therefore,  a  more  rapid  inflow  and 
rising  of  air.  A  cyclonic  storm  has  been  called  a  great  engine, 
furnishing  some  of  its  own  energy  as  the  vapor  condenses. 


Fig.  420.  —  Photograph  of  a  tornado  at  Mt.  Morris,  111. 


iuuiit  mwii-t'w  Tir  11       f 


Fig.  421.  — a  waterspout  off  Marthas  Vineyard,  Mass. 


Via  422  —Destruction  done  by  the  tornado  at  Mt.  Morris  (Fig.  420) .    In  the  Poof  of  tb»  UDseF 
'    figure,  notice  the  laths  driven  through  boards  bv  the  force  of  the  wind. 


WINDS   AND   STORMS. 


26? 


Summary 

As  high  and  l^^o 
pressure  area.^ 
pass,  the  ivinds 
vary  in  direction^ 
the  lows  bringing 
warm  air,  clouds^ 
and  rain,  the 
highs  cool,  clear 
air  settling  from 
aloft.  The  rain 
of  cyclonic  storms 
is  caused  (i)  by 
the  rising  of  air, 
(3)  by  its  passage         ^'''-  *-^- "  ^^^^^S^^^^  «f  ^  distant  thunder  storm. 

from  ivarmer  to  cooler  regions,  and  (3)  by  its  rising  over  highlands. 

TJie  heat  liberated  by  condens- 
ing vajoor  causes  the  air  to  rise 
with  increasing  energy,  and, 
therefore,  over  water  storms 
increase  in  vigor. 

179.    Thunder  Storms 
and     Tornadoes.  —  (A) 

Thunder  Storms.  —  These 
are  local  storms  which  de- 
velop in  low  pressure  areas, 
usually  in  the  southern  por- 
tion where  warm,  humid 
air  is  slowly  moving  from 
the  south.  On  such  mug- 
gy, oppressive  days  the  air 
is  not  rising  fast  enough 
to  form  a  blanket  of  clouds; 
as     the     ground     is 


eORMAy    4    CO.,    N.Y» 

Fig.  424.  —  Part  of  a  weather  map,  July  i.,jf 

16,  1891,  showing  a  low  pressure  area  '  .  i        i  i 

with  thunder  storms   (indicated  by  warmed  during  the  day,  the 

arrows)  in  its  southern  part.  humid  air  riscs,  and  patches 


268  NEW  PHYSICAL   GEOGRAPHY, 

of  cumulus  clouds  appear  (p.  248).  As  the  day  passes  these 
grow  larger  and  darker,  rising  as  masses  of  rolling,  surging 
cloud,  perhaps  a  full  mile  above  the  level  base. 

Rain  finally  falls  from  these  clouds,  and  thunder  and  light- 
ning are  produced.  The  lightning  is  an  electric  spark,  pass- 
ing from  cloud  to  cloud,  or  from  the  clouds  to  the  earth,  the 
electricity  being  produced  when  the  air  currents  are  swirling 
violently  about  and  the  vapor  rapidly  condensing.  Thunder 
is  the  noise  caused  by  the  spark,  and  its  rolling  is  the  result 
of  echoes  among  the  clouds. 

Thunder  storms  are  often  small,  perhaps  only  a  few  hundred 
yards  in  area ;  but  sometimes  they  are  50  to  100  miles  long,  15  to 
25  miles  broad,  and  3  to  5  miles  high.  They  travel  eastward  in 
the  west  winds  at  the  rate  of  20  to  50  miles  an  hour,  and  may  last 
from  2  to  10  hours  before  dying  out.  The  rain  is  heavy,  the  winds 
often  strong,  and  the  lightning  destructive.  On  the  borders  of 
thunder  storms,  hail  frequently  falls  (p.  250). 

Thunder  storms  occur  in  other  places  where  warm,  humid  air  is 
rising  to  a  level  at  which  its  vapor  rapidly  condenses.  For 
example,  they  are  of  almost  daily  occurrence  in  the  belt  of  calms. 
Around  mountains,  too,  as  the  air  rises  on  a  hot  day,  clouds  often 
gather  and  develop  into  thunder  storms.  In  arid  lands  these 
storms  are  sometimes  accompanied  by  so  rapid  condensation  of 
vapor  and  so  heavy  rain  that  they  are  called  "  cloudbursts.'^ 

Summary.  —  Tliunder  storms  are  caused  by  the  rising  of  warm, 
humid  air  in  loio  pressure  areas,  usually  in  the  southern  portion  ;  they 
are  over-developed  cumidus  clouds.  They  also  occur  in  the  belt  of 
calms,  and  where  air  is  rising  around  mouiitains. 

(B)  Tornadoes.  —  Tornadoes  (Fig.  420)  develop  in  the 
southern  portion  of  low  pressure  areas  under  conditions  simi- 
lar to  those  causing  thunder  storms.  The  warm,  humid,  lower 
layers  of  air,  brought  by  south  winds,  have  above  them  cooler 
layers  moving  from  the  west.  As  the  lower  air  warms  and 
rises,  a  whirl  starts  around  the  center  of  rising,  and  the  winds 
blow  with  great  force.    Like  thunder  storms,  tornadoes  often 


WINDS  AND   STORMS.  269 

occur  in  groups,  perhaps  a  score  or  more  developing  at  one 
time,  and  not  very  far  apart.  Heavy  rain  and  liail  fall  at 
the  margin  of  the  whirl,  and  thunder  and  lightning  occur. 

The  winds  of  the  tornado  whirl  are  so  strong  that  houses  are 
overturned,  heavy  bodies  picked  up  and  carried  long  distances, 
trees  uprooted,  and  paths  cut  through  the  forest.  In  the  center  of 
the  whirl  there  is  a  partial  vacuum,  and,  as  it  passes,  the  air  inside 
of  houses  expands  with  such  force  as  to  blow  out  the  windows,  and 
even  the  walls.  The  path  of  great  destruction  is  only  a  few  score 
yards  wide,  though  it  may  reach  a  length  of  several  miles  before 
the  tornado  dies  out.  Although  the  passage  of  a  tornado  lasts  but 
a  minute  or  two,  its  work  of  destruction  is  so  complete  (Fig.  422) 
that  tornadoes  are  much  dreaded ;  and,  in  regions  visited  by  them, 
holes,  called  "  cyclone  cellars,"  are  made  in  the  ground  for  shelter. 

Fortunately  tornadoes  do  not  occur  everywhere.  They  are 
especially  abundant  in  the  Mississippi  valley.  In  that  level,  open 
country  it  is  easily  possible  for  warm,  humid  air  from  the  Gulf  of 
Mexico  to  slide  in  under  the  cooler,  upper  air  and  thus  bring 
about  the  unstable  conditions  which  are  so  favorable  to  tornado 
formation.  They  do  not  develop  in  arid  countries,  because  the 
air  is  not  humid  enough ;  nor  are  they  common  in  mountainous 
or  hilly  lands,  because  the  irregular  surface  causes  a  mixture  of 
warm  and  cool  air  layers.  They  rarely  occur  east  of  the  northerr 
Appalachians. 

Summary.  —  Warm,  humid  air,  creeping  under  cooler  layers  in 
the  southern  part  of  low  pressure  areas,  especially  on  the  level  p)lains, 
causes  an  ^instable  condition  ;  and  at  times,  as  the  air  rises,  the 
in-moving  winds  start  a  violent  whirl,  forming  a  tornado. 

(C)  Waterspouts.  —  At  sea  conditions  favoring  tornadoes  produce 
waterspouts  (Fig.  421).  In  their  center  the  water  is  raised  in  a  low 
cone,  and  some  salt  water  is  actually  carried  up  into  the  spout. 

Summary.  ■ —  Waterspouts  are  tornadoes  at  sea. 

180.  Hurricanes  and  Typhoons.  —  Very  violent  storms, 
known  in  the  Pacific  as  typhoons^  and  in  the  Atlantic  as  hur- 
ricanes, develop  in  the  tropical  zone  and  move  into  the  temper- 


270 


NEW  PHYSICAL  GEOGRAPHY. 


ate  zones.  On  passing  into  the  cooler  temperate  zones  they 
become  larger  and  less  violent,  and  then  closely  resemble 
cyclonic  storms.  The  path  followed  by  the  Atlantic  hur- 
ricanes is  usually 
across  the  West  In- 
dies, off  the  coast 
of  the  southern  At- 
lantic States,  then 
out  to  sea,  curving 
eastward  under  the 
influence  of  the 
earth's  rotation. 
Sometimes  they  de- 
part from  this  course 
(Fig.  427),  visiting 
the  Gulf  coast  and 
even  the  GreatLakes. 
The  typhoons  of  the 
Pacific    and    Indian 


Fig.  425.  — Diagram  of  a  hurricane,  showing  direc- 
tion of  movement  (long  arrow),  rain  area 
(shaded) ,  and  winds  eddying  toward  low  pres- 
sure center,  C. 


oceans  have  various  courses,  some  of  those  in  the  northern 
hemisphere  passing  over  the  Philippines. 

These  storms  start  by  the  rising  of  warm,  humid  air  in  the 
torrid  belt,  forming  a  whirl  similar  to  that  in  a  tornado, 
though  much  larger 
(Fig.  426).  They 
originate  on  the 
ocean  rather  than  on 
the  land,  because  the 
humid  air  over  the 
sea  supplies  much 
vapor,  which,  on  con- 
densing, liberates  heat  that  warms  the  air  and  causes  it  to 
rise  still  more  rapidly. 

The  pressure  is  very  low  in   the  center,  though  not  ap- 
proaching a   vacuum.     Toward   this   center   violent   winds 


Fig.  426.  —  Graphic  sketch  to  illustrate  wind 
movement  in  a  hurricane. 


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WINDS  AND   STORMS,  .  271 

blow  (Figs.  425-428),  often  with  such  force  as  to  overturn 
trees  and  houses.  Towns  have  been  devastated  and  many 
vessels  lost,  as  at  Samoa  in  1889,  when  several  war  ships 
were  destroyed  during  a  typhoon.  Along  the  Atlantic  coast 
of  the  United  States  the  most  violent  storms  are  hurricanes, 
which  often  leave  the  coast  strewn  with  wreckage. 

Heavy  rains,  vivid  lightning,  and  loud  thunder  accompany  these 
storms.  With  them  also  travels  a  wave  of  high  water,  which,  ad- 
vancing on  low  coasts,  causes  much  destruction,  destroying  kouses, 
towns,  and  life.  It  was  one  of  these  waves,  rising  over  Galves- 
ton, that,  together  with  the  winds,  caused  such  terrible  destruction 
in  1900,  killing  thousands  of  people  and  almost  destroying  the 
city  (Fig.  429).  Such  a  wave  is  due  to  two  causes:  (1)  drifting 
of  water  toward  the  storm  center  by  the  spirally  in-blowing 
winds  (Figs.  425-428) ;  (2)  rising  of  water  in  the  center  because 
the  weight  of  the  air  there  is  less  than  in  the  ring  surrounding  it. 

Most  hurricanes  occur  in  late  summer  and  early  fall,  because 
then  the  belt  of  greatest  heat  is  farthest  north.  At  the  equator, 
winds  are  not  turned  by  the  influence  of  rotation ;  but,  as  the  dis- 
tance from  the  equator  increases,  they  are  turned  more  and  more. 
Whirls  can  develop  only  when  the  winds  are  turned  to  one  side 
so  as  to  start  a  spiral  movement  around  the  center  of  rising. 
For  this  reason  hurricanes  cannot  start  at  or  near  the  equator ;  but 
they  can  start  in  the  hot  belt  when  it  has  migrated  some  distance 
from  it.  In  the  North  Atlantic  the  period  when  the  belt  of  calms 
is  farthest  from  the  equator  is  in  late  summer,  and  then  hurri- 
cane whirls  start  in  the  rising  air. 

Summary.  —  Hurricanes  and  typhoons  are  violent  ivhirls,  starting 
in  the  torrid  zone,  and  resembling  tornadoes,  though  larger  and  less 
violent.  They  start  over  the  ocean  .because  of  the  great  amount  of 
vapor,  ivhose  condensation  supplies  heat  ivhich  causes  more  rapid 
rising.  Their  fierce  ivinds,  and  the  ivater  wave  which  accompanies 
them,  cause  great  destruction.  They  occur  late  in  summer,  or  early 
in  autumn,  when  the  belt  of  calms  is  farthest  from  the  equator,  be- 
cause then  the  effect  of  rotation  can  deflect  the  winds  arid  sf,g,rt  the 
spiral  movement  which  cctuses  the  ivhirl. 


272  NEW  PHYSICAL   GEOGRAPHY, 


Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  — 173.  Relation  between  Winds  and  Air  Pres- 
sure.—  Air  columns;  effect  of  heat;  low  pressure;  high  pressure; 
cause  of  winds;   barometric  gradient;  strong  winds. 

174.  Sea  and  Land  Breezes.  —  Cause  of  sea  breezes ;  effects ;  land 
breezes. 

175.  Mountain  Valley  Breezes.  —  Movement  down  valleys;  up  valleys. 

176.  Monsoon  Winds.  —  Place  of  best  development ;  summer  monsoon ; 
winter  monsoon  ;  importance  to  sailing  vessels ;  reason  for  lack  of  devel- 
opment elsewhere ;  condition  in  northeastern  United  States. 

177.  Wind  Systems  of  the  Earth. —  (A)  Comparison  with  a  Stove:  air 
movements  in  room  heated  by  stove;  on  earth.  (B)  Effect  of  Rotation: 
right-hand  deflection;  left-hand  deflection.  (C)  Belt  of  Calms:  cause; 
doldrums ;  migration.  (D)  Trade  Winds  :  steadiness ;  deflection  ;  south- 
east trades ;  northeast  trades ;  change  in  position  ;  relation  of  Asiatic 
monsoons  to  trades.  (E)  Antitrades  :  upper  outflow;  direction  ;  proof  of 
existence.  (F)  Prevailing  Westerlies :  source  of  air ;  circumpolar  whirl ; 
effect  of  rotation  ;  prevailing  westerlies ;  interference  with  winds  ;  west- 
erlies over  Southern  Ocean;  in  northern  hemisphere;  high  in  the  air. 
(G)  Horse  Latitudes :  location ;  settling  air ;  condition  of  winds ;  shifting 
of  belts. 

178.  Cyclonic  Storms.  —  (A)  Characteristics :  low  pressure  area ;  iso- 
bars; winds;  rain;  cyclonic  storm ;  movement.  (B)  Anticyclones:  pres- 
sure; winds;  sky;  name;  movement.  (C)  Succession  of  Cyclones  and 
Anticyclones:  regular  succession;  weather  changes;  places  of  origin; 
paths ;  weak  lows  ;  iri-egularities.  (D)  Cause  of  Cyclonic  Storms  :  com- 
parison with  river  eddies  ;  theory  of  heat  origin  ;  theory  of  wave  origin  ; 
relation  of  eddies  to  low  pressure.  (E)  Influence  of  Cyclones  and  Anti- 
cyclones on  Weather:  (a)  Winds,  —  variation  in  direction;  deflection; 
variation  in  force ;  rising  air  in  lows ;  settling  in  highs,  (h)  Tempera- 
ture,—  south  winds  ;  north  winds ;  settling  air ;  passage  of  lows  ;  of  highs ; 
radiation,  (c)  Rain, — reason  for  dryness  in  highs;  effect  of  rising  in 
lows;  other  causes  for  rain  ;  source  of  vapor  ;  northeast  storms  ;  effect  of 
liberation  of  heat;  storms  over  water. 

179.  Thunder  Storms  and  Tornadoes.  —  (A)  Thunder  Storms :  place  of 
occurrence  in  low  pressure  areas ;  cause ;  growth  ;  lightning ;  thunder ;  size ; 
path;  rate  of  movement ;  occurrence  elsewhere;  cloudbursts.  (B)  Tor- 
nadoes: favoring  conditions ;  the  whirl;  comparison  with  thunder  storms; 
effect  of  winds;  condition  in  center;  path;  time  of  passage;  cyclone 
cellars;  occurrence  in  Mississippi  valley;  absence  in  other  sections. 
(C)   Waterspouts., 


WINDS  AND   STORMS.  273 

180.  Hurricanes  and  Typhoons. — Typhoons;  hurricanes;  places  of 
development;  movement  into  temperate  zones;  paths  followed;  cause; 
reason  for  development  over  the  sea;  accompanying  phenomena;  effects 
of  water  wave  ;  cause  of  wave ;  time  of  occurrence ;  explanation  of  this. 

Questions.  —  173.  What  is  the  cause  of  wind?  What  is  barometric 
gradient?     When  are  winds  strong? 

174.  Explain  sea  breezes ;  land  breezes. 

175.  Explain  the  day  and  night  breezes  of  mountain  valleys. 

176.  Where  are  monsoons  best  developed  ?  Explain  them.  What  is 
the  condition  in  northeastern  United  States  ? 

177.  (A)  Compare  the  circulation  in  a  room  heated  by  a  stove  with 
that  of  the  earth.  (B)  in  what  direction,  and  why,  are  winds  turned 
from  a  straight  course?  (C)  What  is  the  condition  in  the  belt  of  calms? 
Why  does  it  change  position  ?  (D)  What  are  the  directions  of  the  trade 
winds?  Why?  What  effect  has  the  migration  of  the  belt  of  calms? 
Why  are  the  monsoons  so  well  developed  in  Asia?  (E)  What  is  the 
direction  of  the  antitrades  ?  How  is  this  known  ?  (F)  What  is  the  cir- 
cumpolar  whirl?  W^hat  is  the  direction  of  the  winds?  Why?  What  are 
the  prevailing 'westerlies?  What  interferes  with  the  regular  winds? 
How  do  the  westerlies  of  the  northern  and  southern  hemispheres  differ? 
(G)  What  are  the  conditions  in  the  horse  latitudes  ?     Why  ? 

178.  (A)  What  is  a  low  pressure  area  ?  What  are  isobars  ?  A  cyclonic 
storm?  State  its  characteristics.  (B)  What  are  anticyclones  ?  Contrast 
with  cyclonic  storms.  (C)  What  changes  accompany  the  highs  and 
lows  ?  What  paths  are  pursued?  What  irregularities  are  noticed?  (D) 
Compare  cyclonic  storms  with  eddies  in  a  river.  State  the  two  theories 
for  these  storms.  What  facts  favor  one  rather  than  the  other?  (E) 
What  is  the  nature  of  the  winds  in  high  and  low  pressure  areas?  What 
changes  in  temperature  occur  as  these  areas  pass  over  a  region  ?  What 
are  the  causes  of  rain  in  the  cyclonic  storms?  Why  do  storms  commonly 
increase  in  violence  when  passing  over  large  water  bodies? 

179.  (A)  Under  what  conditions  do  thunder  storms  appear  in  low 
pressure  areas?  Why?  What  is  the  lightning?  The  thunder?  What 
are  the  characteristics  of  these  storms  ?  Where  else  do  thunder  storms 
occur?  (B)  Under  what  conditions  do  tornadoes  develop?  What  are 
some  results  of  tornadoes?  Where  are  they  most  common?  Why?  In 
what  situation  are  tornadoes  rare?     (C)  What  are  waterspouts? 

180.  What  are  hurricanes?  Typhoons  ?  What  paths  do  they  follow  ? 
WTiy  do  they  start  over  the  sea?  What  destruction  do  they  accomplish? 
Give  instances.  What  destruction  is  done  by  the  water  wave  ?  What  is 
the  cause  of  this  wave?  When  are  these  storms  most  common?  Why 
at  that  season  ? 


274  NEW  PHYSICAL   GEOGBAPHT. 

Suggestions.  —  (1)  Recall  tlie  previous  experiments  on  convection 
(Chapter  XII,  10).  (2)  Open  a  window  on  a  cold  day  when  no  wind 
is  blowing.  Why  does  the  cold  air  enter  the  room?  (3)  Keep  a  record 
of  the  wind  direction  for  twenty  days.  How  many  days  did  the  wind 
blow  from  each  of  the  four  quarters  (north,  east,  south,  and  west)  ? 
For  the  same  period  keep  a  record  of  the  direction  that  the  higher 
clouds  are  moving.  How  many  days  do  they  move  from  each  quarter  ? 
(4)  On  an  outline  map  make  a  sketch  of  the  winds  of  the  globe  simi- 
lar to  Fig.  408.  Make  a  sketch  to  show  the  change  in  position  of  the 
belt  of  calms  (Figs.  439,  440).  (5)  If  the  instruments  are  available, 
keep  a  record  of  the  wind  direction  and  force,  humidity,  temperature, 
clouds  and  rain,  and  barometric  pressure  (Appendix  G).  Tell  when 
cyclonic  storms  and  anticyclones  are  passing,  and  carefully  record  the 
relation  between  air  pressure  and  the  other  phenomena.  From  your  obser- 
vations predict  the  weather  for  the  following  day.  (6)  Study  weatlier 
maps  (Appendix  H).  (7)  With  apparatus  obtained  from  the  physics  labo- 
ratory make  an  electric  spark.  This  is  a  lightning  flash  on  a  small  scale, 
and  the  noise  is  thunder.  A  similar  flash  and  noise  may  often  be  noticed 
as  a  trolley  car  passes.  (8)  If  thunder  storms  occur,  keep  a  record  of 
all  the  phenomena  and  report  upon  them.  (9)  Read,  say  in  Harper's 
Wp.ekly  for  the  autumn  of  1900,  an  account  of  the  destruction  of  Galves- 
ton. Be  on  the  outlook  next  fall  for  newspaper  reports  of  hurricanes  or 
typhoons;  also,  next  summer,  for  reports  of  tornadoes. 

Reference  Books.  —  Harrington,  Rainfall  and  Snoiv  of  United  States, 
Bulletin  C,  U.  S.  Weather  Bureau,  Washington,  D.C.,  1894;  Ferrel, 
Popular  Treatise  on  the  Wind,  Wiley  &  Sons,  New  York,  1889,  $4.00; 
Finley,  Tornadoes,  Hine,  New  York,  1887,  $1.00.  (See  also  references 
at  end  of  Chapter  XII.) 


CHAPTER   XIV. 

WEATHER   AND    CLIMATE. 

181.  Difference  between  Weather  and  Climate.  —  Weather 
refers  to  daily  changes  in  temperature,  wind,  clouds,  and 
rain.  Climate  is  the  average  result  of  these  weather  changes. 
For  example,  certain  parts  of  the  tropical  zone  are  said  to 
have  a  rainy  climate.  This  does  not  mean  that  it  rains  every 
day,  but  that,  though  the  weather  on  some  days  is  clear,  on 
still  more  it  is  rainy.  Thus  the  average  condition,  or  the 
climate,  is  rainy. 

The  following  are  some  of  the  more  important  kinds  of 
climate:  dry,  hot  desert  climates;  hot,  rainy  climates,  as  in 
the  belt  of  calms;  damp,  equable  ocean  climates;  extreme  and 
variable  climates,  common  in  the  interior  of  continents;  and 
frigid  climates.  The  greater  part  of  the  United  States  has  a 
variable  climate.  These  different  climates,  and  the  reasons 
for  them,  can  best  be  understood  by  studying  the  conditions 
in  various  parts  of  the  world. 

Summary.  — Climate  is  the  average  of  iceather,  ivhich  is  the  daily 
condition  of  temperature,  ivind,  clouds,  and  rain.  There  are  a  num- 
ber of  very  different  climates  on  the  earth. 

182.  Zones  of  Heat.  —  (A)  The  Five  Zones.  —  The  most 
widespread  cause  for  variations  in  climate  is  the  distribution 
of  sun's  heat  from  equator  to  poles.  This  results  from  the 
differences  in  angle  at  which  the  sun's  rays  reach  the  earth 
in  different  latitudes  (p.  239).  From  this  has  arisen  the 
common  division  of  the  earth  into  five  climatic  zones,  —  two 
frigid,  two  temperate,  and  one  torrid,  or  tropical  (Fig.  430). 

276 


276 


NEW  PHYSICAL    GEOGRAPHY, 


It  is  customary  to  draw  the  boundaries  between  tbese 
zones  of  heat  alono-  the  parallels  of  latitude;  but  the  actual 

boundaries    are    by 
^!"^^.  no  means   so    regu- 

lar. Indeed,  there 
are  some  portions 
of  the  torrid  zone 
that  have  as  low 
temperature  as 
parts  of  the  frigid 
zones;  and  some 
parts  of  the  tem- 
perate zones  have 
summer  climates 
that  are  quite  tor- 
rid. Several  reasons 
.o^      ^,     ^  for  these  irregulari- 

FiG.  430. —  ihe  five  zones,  showing,  also,  how  on       .  +i        f   11 

highlands  a  frigid  climate  may  extend  even  into     tieS   are   tiie    lOiiOW- 


the  tropical  zone. 


ing  influences. 


Summary.  —  Oiving  to  the  angle  at  ivJiicJi  the  su7i^s  rays  reach  dif- 
ferent latitudes,  the  earth  may  be  divided  into  foe  zones;  but,  for  a 
number  of  reasons,  the  actual  boundaries  of  the  zones  are  irregular, 

(B)  Influence  of  Altitude.  —  One  important  cause  for 
irregularities  in  the  boundaries  of  the  heat  zones  is  altitude. 
The  climate  of  highlands  is  cooler  than  that  of  neighboring 
lowlands  (p.  240).  The  isothermal  charts  ^  (Figs.  431-434) 
show  numerous  cases,  as  in  the  Rocky  Mountains,  where  the 
isotherms  are  bent  toward  the  equator  in  crossing  higlilands. 
The  influence  of  altitude  is  also  well  shown  along  the  Pacific 

^  An  isotherm  is  a  line  connecting  places  having  the  same  average  tempera- 
ture. An  isothermal  chart  is  one  showing  these  isotherms  for  a  given  area 
(as  the  world,  the  United  States,  or  a  state)  for  a  certain  period  of  time. 
A  chart  for  the  year  has  isotherms  passing  through  places  whose  average 
temperature  for  the  year  is  the  same  ;  a  chart  for  January  averages  all  thtj 
temperatures  for  that  period,  etc. 


-so 


-30 


:{  '     leo  160  jzo  eo  4o.  o  4o  ao  izo 

Fig.  431,  —  Isothermal  chart  of  the  world  for  January. 


Fig.  432. — Isothermal  chart  of  the  world  for  July. 


Fig.  433.  —  Isothermal  chart  of  United  States  for  January. 


Fig.  134.  — Isothermal  chart  of  Uftite4  States  for  July. 


LEATHER  AND   CLIMATE. 


277 


slope  (Fig,  433),  where  winds  from  the  equable  ocean  blow 
upon  a  rising  coast,  with  mountains  extending  north  and 
south.  Along  this  coast  the  climate  is  warm  and  equable ; 
but  on  the  mountain  slopes  the  temperature  descends. 
Therefore  the  isotherms  extend  north  and  south  instead  of 
east  and  west,  as  is  commonly  the  case. 

Summary.  —  Highlands  are  cooler  than  neighboring  lowlands. 
Tlierefore  highlands  cause  the  isotherms,  or  lines  connecting  x)laces 
having  the  same  average  temperature,  to  extend  irregularly. 

(C)  Influence  of  Water.  —  Distance  from  water  (p.  238)  is 
another  cause  for  variation  in  temperature.  Oceanic  islands 
have  cooler  summers  and  Avarmer  winters  than  the  mainland 
in  the  same  latitude  ;  and  seacoasts  have  more  equable  cli- 
mates than  interiors.  This  is  clearly  illustrated  by  compar- 
ing the  isotherms  in  the  interior  and  on  coasts  of  continents. 

Examine  Figs.  433  and  434,  for  example,  to  see  how  much 
difference  there  is  in  January  and  July  between  Minnesota,  the 
state  of  Washington,  and  Nova  Scotia.     Find  other  illustrations 


fiORHOY  &  CO.,  N.f. 


Scale  of  Temperature 


0l»20.    20to50.  50to9a.90toai0.110t«120 

Fig.  435.  —  To  show  the  annual  mean  (average)  range  in  temperature  tor  the  world. 


278  NEW  PHYSICAL    GEOGRAPHY, 

on  the  world  charts  (Figs.  431,  432).  Study  the  chart  of  tempera- 
ture range  (Fig.  435)  to  see  where  there  are  great  and  small 
ranges.  Contrast  the  range  over  the  Atlantic  with  that  over 
Asia  and  America ;  and  the  range  over  the  Southern  Ocean  with 
that  over  the  lands  of  the  northern  hemisphere. 

Summary.  —  Oceans  and  coasts  have  a  far  more  equable  climate 
than  the  interiors  of  continents. 

(D)  Influence  of  Winds.  —  The  influence  of  winds  in 
causing  irregularity  in  the  isotherms  is  best  illustrated,  on  a 
large  scale,  where  winds  blow  from  water  upon  land,  as  in 
northwestern  United  States  and  Europe  (Figs.  431-434). 
In  these  places  the  prevailing  west  winds,  influenced  by  the 
water  over  which  they  pass,  moderate  the  cold  of  winter  and 
the  heat  of  summer.  It  is  for  this  reason  that  in  western 
Europe  agriculture  thrives,  and  large  cities  are  found  in  lati- 
tudes that,  in  eastern  North  America,  are  frigid  and  almost 
uninhabited.  London  is  in  the  same  latitude  as  southern 
Labrador,  and  St.  Petersburg  as  northern  Labrador.  For  the 
same  reason,  the  January  temperature  at  San  Francisco  is  the 
same  as  that  at  Charleston,  S.C.  (5°  farther  south),  while 
the  July  isotherm  is  that  of  Halifax  (6°  farther  north). 

Summary.  — Prevailing  winds  iiifluence  the  temperature,  the  most 
pronounced  influence  being  where  winds  from  the  ocean  prevail,  thus 
carrying  the  equable  temperatures  of  the  water  upon  the  land. 

(E)  Influence  of  Ocean  Currents.  —  Ocean  currents  and 
drifts  bear  water  from  one  zone  to  another  (p.  193).  Winds 
blowing  over  these  currents  have  their  temperature  influenced, 
and,  blowing  upon  the  lands,  bear  to  them  some  of  the  warmth 
or  cold  brought  by  the  currents  from  other  zones. 

This  effect  of  ocean  currents  is  well  illustrated  in  the  North 
Atlantic  (Figs.  320,  431,  432).  The  great  northward  bend  of 
the  isotherms  off  the  European  coast  shows  the  influence  of  the 
warm  west  wind  drift  (Fig.  338).  This  influence  is  least  notice- 
able in  summer  when  the  sun  has  warmed  the  surface  water.     Off 


WEATHER  AND  CLIMATE  279 

iiorthea^stern  North  America,  the  cold  Labrador  current  bends 
the  isotherms  toward  the  equator.  Therefore,  the  isotherms  are 
crowded  together  on  the  American  coast  and  spread  apart,  fan- 
shaped,  on  the  European  coast.  In  other  words,  there  are  much 
greater  differences  in  temperature  in  a  short  distance  in  eastern 
America  than  in  western  Europe.  Notice  also  the  influence  of 
ocean  currents  on  the  isotherms  along  the  west  coasts  of  the 
United  States,  South  America,  and  Africa. 

Summary.  —  Ocean  currents  warm  or  cool  the  air  over  them  ;  mov- 
ing as  ivinds  this  air  transfers  the  influence  of  the  currents  to  the  land. 
Tliis  is  ivell  illustrated  in  the  North  Atlantic, 

(F)  Influence  of  Topography.  — Hills  and  valleys  have  an 
effect  of  a  local  nature  on  climate.  Mountains  produce  far 
more  widespread  effects.  By  shutting  off  winds,  mountain 
barriers  influence  the  climate  of  places  behind  them.  Thus, 
while  the  Pacific  slope  of  United  States  has  an  equable  cli- 
mate, the  country  farther  east,  being  cut  off  from  ocean  winds 
by  the  mountains,  has  hotter  summers  and  colder  winters 
than  the  coast  lands. 

The  subtropical  climate  of  Italy,  southern  Spain,  and  France 
is  partly  due  to  the  influence  of  topography.  The  waters  of  the 
Mediterranean  are  warm ;  the  Alps  and  other  mountains  shut  out 
the  cold  north  winds;  and  they  interfere  with  south  winds  which 
might  bear  away  warmth  from  the  Mediterranean.  Therefore,  in 
this  region,  oranges  and  palms  grow  (Fig.  443)  in  the  latitude  of 
Boston,  New  York,  and  other  places  in  the  United  States  which 
are  visited  by  killing  frosts  for  several  months  of  the  year. 

Summary.  —  Hills  and  valleys  have  a  local  influence  on  climatef 
and  mountains  far  greater  effects,  especially  in  shutting  out  ivinds. 

CLIMATIC   BELTS   OF   THE  TORRID  ZONE. 

183.  Belt  of  Calms  (Fig.  408).— The  vertical  position  of 
the  sun  in  the  equatorial  belt  of  calms  (p.  259)  causes  the 
climate  to  be  hot  (p.  240).     This  belt  is  also  a  very  rainy 


280 


NEW  PHYSICAL   GEOGRAPHT, 


one  (Figs.  436-440,  444),  because  the  rising  air  soon  reaches 
an  elevation  where  its  vapor  condenses  (p.  268). 

The  weather  of  the  belt  of  calms  is  monotonously  uniform. 
On  the  ocean,  or  on  oceanic  islands,  the  air  grows  warmer  each  day 
after  the  sun  rises ;  and  from  the  clouds  which  form,  and  which 
often  develop  into  violent  thunder  storms,  heavy  rain  falls. 
During  the  night  the  humid  air  is  still  warm,  for  there  is  not 
enough  radiation  to  cool  it.  Both  day  and  night  there  is  an 
absence  of  steady  winds,  and  sailing  vessels  are  often  becalmed 
for  days.     These  conditions  are  repeated  with  marked  regularity. 

The  daytime  temperatures 
are  higher  on  the  land,  and 
winds  are  often  caused  by 
differences  in  temperature, 
for  example,  along  the  coast 
where  sea  breezes   blow  (p. 

The  rainfall  is  so  heavy 
that  dense  forests  thrive  on 
the  land,  and  the  air  within 
these  is  reeking  with  mois- 
ture. So  warm  and  damp  is 
the  climate  that  it  is  difficult 
to  work ;  the  clearing  away 
Fig.  436.  — Rainfall  of  calm  and  trade-wind  of  vegetation  for  planting  is 
belts  of  America.  such  a  task  that  it  is  rarely 

undertaken;  and,  in  fact, 
there  is  little  need  for  doing  so,  since,  with  little  labor,  the  forest 
plants  yield  abundant  food.  For  these  reasons  the  tropical  forest 
is  inhabited  by  races  depending  directly  upon  nature  for  food, 
who,  having  little  ambition  for  improving  their  condition,  have 
made  little  progress  toward  civilization. 

r  

Summary.  —  The  belt  of  calms  has  a  hot,  Jiumid  climate  tvith  a 
general  absence  of  winds.  TJie  heat  and  humidity  cause  a  ranh 
''jrowth  of  t7'opical  forest,  but  discourage  progress  among  mankind. 

184.   Rainy  Trade- wind  Belts.  —  To  the  north  and  south  oJ 


LEATHER  AND   CLIMATE, 


281 


the  belt  of  calms  the  trade  winds  (p.  259)  blow  toward 
warmer  regions.  Vapor  is  therefore  constantly  rising  into 
them,  because,  the  warmer  the  air,  the  more  vapor  possible 
(p.  244).  So  much  fresh  water  is  thus  removed  that 
the  sea  is  made  more  salt 
(p.  181)  where  the  trade 
winds  blow.  These  winds 
bear  such  quantities  of  vapor 
that,  when  they  blow  over 
rising  land,  where  the  air 
rises  and  cools,  vapor  is  con- 
densed. East-facing  coasts, 
against  which  the  trade  winds 
blow,  are,  therefore,  very 
rainy  (Figs.  436-440,  444). 

The     east     coast     of      South       ^^^-  437.  —  Rainfall    of   calm,    trade- 
.  --1,1  4.1.         J  i.1,  wind,  and  westerly  belts  of  Aus^ 

America,  both,  north  and.  south  tralasia 

of  the  equator  (Fig.  436),  the 

East  and  West  Indies,  northeastern  Australia  (Fig.  437),  and 
southeastern  Africa  (Fig.  438)  have  heavy  rains,  because  the 
trade  winds  blow  upon  them  from  the  sea.  These  places  have  a 
tropical  forest,  resembling  that  of  the  belt  of  calms.  Mountain- 
ous oceanic  islands  in  the  trade-wind  belt,  like  the  Hawaiian 
Islands,  have  heavy  rains  on  the  eastern  or  windward  side  while 
the  opposite  side  has  a  dry  climate. 

Summary.  —  East-facing  coasts  in  the  trade-wind  belts  have  a 
rainy  climate,  because,  as  the  damp  air  cools  in  rising  over  the  land, 
some  of  the  vapor,  evaporated  from  the  ocean,  is  precipitated, 

185.  Desert  Trade- wind  Belts. — In  the  trade-v/ind  belts 
arid  conditions  are  far  more  common  than  rainy  ;  in  fact,  the 
trade  wunds  furnish  the  most  important  caune  for  deserts. 
They  take  up  vapor  in  passing  over  the  land  for  the  same 
reason  as  on  the  ocean  ;  but  there  is  so  little  moisture  to  be  ob- 
tained on  land  that  they  become  very  dry  winds,  into  which 


282 


NEW  PHYSICAL  GEOGRAPHY. 


FiQ.  438.  —  Rainfall  of  calm  and  trade-wiud 
belts  of  Africa. 


vapor  rises  wherever  possible.  This  leaves  so  little  water 
for  plants  that  the  land  is  made  desert ;  but  even  in  the 
driest  desert  air  there  is  some  vapor,  and  rain  occasionally 
falls.     In  the  Mohave  desert  of  Arizona  the  rainfall  is  less 

than  two  inches  a  year. 

Because  of  these  con- 
ditions both  north  and 
south  of  the  equator, 
there  is  a  broad  belt  of 
arid  and  desert  country 
extending  almost  com- 
pletely across  the  conti- 
nents, though  on  east-fac- 
ing coasts  interrupted  by 
rainy  belts.  These  desert 
belts  include  parts  of  Aus- 
tralia (Fig.  437),  South 
Africa  (Fig.  438),  southern  South  America  (Fig.  436),  and 
southwestern  United  States  (Fig.  442);  but  the  largest  desert 
tract  is  in  the  great  land  area  of  northern  Africa  and  Asia. 
Commencing  in  western  Africa,  there  is  a  series  of  deserts 
extending  far  toward  the  east  coast  of  Asia  (Fig.  444). 
The  great  Sahara  is  a  part  of  this  belt. 

In  many  places  the  deserts  of  the  trade-wind  belts  merge  into 
the  arid  regions  of  the  horse  latitudes  (p.  261).  Here  also  the 
air  is  warming,  and  evaporation,  therefore,  proceeds  rapidly. 

Life  in  the  deserts  presents  a  far  different  picture  from  that  in 
the  tropical  forest.  Only  a  few  species  of  plants  are  adapted  to  life 
amid  the  unfavorable  conditions,  and  even  these  are  scattered  (p. 
342).  Therefore,  the  desert  is  a  barren,  open  country ;  and  neither 
animals  (p.  357)  nor  men  (p.  386)  find  it  a  favorable  place  for  a  home. 
Deserts  are  among  the  most  sparsely  settled  parts  of  the  world. 

The  weather  is  nearly  always  dry,  the  sky  usually  cloudless, 
and  the  winds  often  strong,  blowing  sand  about  (p.  87).  Even 
in  the  temperate  zone  the  days  are  warm,  and  in  summer  hot. 
For  example,  in  the  desert  of  southern  Arizona,  though  far  north 


WEATHER  AND   CLIMATE.  283 

of  tne  tropic  of  Cancer,  the  thermometer  sometimes  rises  to  120^ 
in  the  shade.  The  highest  air  temperature  recorded  (127°)  was 
in  the  Algerian  desert.  But  radiation  is  rapid  in  the  dry  desert 
air,  and  at  night  the  ground  and  air  cool  so  quickly  that  a  blanket 
may  be  necessary  before  morning. 

Summary.  —  WJiere  air  is  growing  warmer,  as  in  the  trade-wind 
and  horse-latitude  belts,  the  climate  is  dry  and  the  land  arid  or 
desert.  Most  of  the  deserts  are  in  these  belts.  Deserts  are  unfavor- 
able to  life,  — plant,  animal,  and  human.  The  desert  climate  is  dry, 
often  ujindy,  and  hot  days  are  folloiued  by  cool  nights. 

186.  Savanna  Belts. — Between  the  rainy  belt  of  calms  and 
the  trade- wind  deserts  there  is,  in  each  hemisphere,  a  region, 
called  the  savanna  belt,  that  has  alternate  dry  and  wet  seasons. 
This  peculiar  climate  is  caused  by  the  migration  of  the  belt  of 
calms  (p.  259).  In  the  hot  season  the  belt  of  calms  migrates 
to  the  savannas  and  there  is  heavy  rain  (Figs.  439,  440)  ;  but 
in  the  opposite  season  the  savannas  are  under  the  influence 
of  the  drying  trade  winds. 

As  a  result  of  these  changes,  the  hot  season  (the  time  of  our 
summer  in  the  northern  hemisphere,  and  of  our  winter  in  the 
southern)  has  copious  rainfall,  and  vegetation  freshens  and  grows 
vigorously  ;  but  in  the  opposite  season  the  ground  is  parched,  and 
vegetation  withers.  The  season  of  drought  is  too  severe  for  many 
forms  of  vegetation,  such  as  trees.  Therefore,  the  savannas  are 
covered  with  those  plants,  such  as  grass  (Fig.  491),  which  are 
able  to  survive  a  period  of  drought  (p.  342). 

The  downes  of  Australia,  the  pai'k  lands  of  Africa,  the  llanos  of 
Venezuela  and  Colombia,  and  the  campos  of  Brazil  are  examples 
of  savannas.  Their  grass  supports  large  numbers  of  plant-eatin% 
animals,  upon  which  flesh-eating  mammals  prey. 

Savannas  are  probably  destined  to  become  the  most  productive 
and  best-settled  lands  in  the  tropical  zone.  The  open  country 
favors  agriculture,  and  the  drought  makes  necessary  some  provi- 
sion for  that  season.  Being  thus  forced  to  industry  and  thrift, 
the  negroes  of  the  savannas  have  become  farmers  and  cattle 
raisers,  and  are  the  most  advanced  blacks  of  Africa. 


284  SEW  PHYSICAL   GEOGRAPHY. 

Summary.  —  TJie  migration  of  the  belt  of  calms  brings  abundan.. 
rain  to  the  margin  of  the  desert  trade-icind  belt  during  the  hot  season^ 
giving  rise  to  alternate  seasons  of  drought  and  rain.  This  makes  such 
regions,  called  savannas,  great  pasture  lands,  well  adapted  to  life. 

187.  The  Indian  Climate.  —  As  a  result  of  the  influence  of 
tlie  monsoons  (p.  250),  parts  of  India  have  a  peculiar  climate 
with  three  well-defined  seasons,  —  the  hot  season,  the  rains, 
and  the  cool  winter.  During  the  hot  season,  which  lasts  from 
April  to  June,  hot,  dry  winds  from  the  land  cause  the  tem- 
perature to  rise  above  100°  in  the  shade.  In  June  the  air 
becomes  calm  and  the  heat  almost  suffocating,  and  every  one 
longs  for  the  summer  monsoon.  When  this  begins,  clouds 
appear,  rain  falls,  and  for  a  month  or  two  rains  are  of  almost 
daily  occurrence,  causing  vegetation  to  grow  profusely. 

A  short  period  of  calm  follows  the  summer  monsoon,  and  again 
the  heat  is  intense ;  but  cool  air  from  the  interior  soon  begins  to 
flow  down  toward  the  sea,  and  by  October  the  winter  monsoon 
is  established.  The  air  is  then  clear  and  cool,  and  by  January, 
in  many  parts  of  India,  fires  are  necessary.  In  February  and  March 
a  sort  of  spring  visits  the  land.  Vegetation  then  bursts  forth,  only 
to  be  withered  by  the  scorching  drought  of  the  hot  season,  which 
postpones  the  real  growing  season  until  the  summer  rains. 

So  heavy  is  the  rainfall  on  the  mountain  slopes  that,  in 
places,  the  soil  is  completely  washed  away.  The  heaviest  rain- 
fall in  the  world  is  at  the  base  of  the  Himalayas  (Fig.  441). 
h\  a  year  there  are  about  500  inches  of  rain  ;  that  is,  if  it 
should  all  stand  where  it  fell,  it  would  form  a  layer  of  40  feet. 
Of  this  amount  about  two  thirds  falls  in  the  five  summer 
month«.  On  a  single  day  there  have  been  40  inches  of  rain, 
or  more  than  falls  in  most  parts  of  the  United  States  in  a  year. 

Summary.  —  The  Indian  climate  consists  of  a  hot  season  (April 
to  Jane) ;  a  rainy  season,  during  the  summer  monsoon  {June  to 
August) ;  and  a  cool  season,  during  the  winter  m.onsoon.  In  jyarts 
of  India  the  rainfall  daring  the  summer  monsoon  is  very  heavy, 
the  rainiest  pjart  of  the  world  being  in  northern  India. 


Ajr 


-m^ 


16- 


■^ 


ZH  LIGHT   RAINFAWL    [\  I 
1  MODERATE-ttl  y 


G.  439.  —  Sketch  map  of  winds  and  rainfall  in 
summer.  Zone  of  greatest  heat  marked  by 
dots,  an  imaginary  line  in  the  center  of  this 
area  being  the  heat  equator. 


m.  440.  —  Sketch  map  of  winds  and  rainfall  in  win- 
ter. Compare  with  Fig.  439  to  see  nature  and 
effect  of  migration  of  wind  belts. 


iiw" 


i^r/ODER-:-  .■         1^^ 

Sl^  1 E  «v  ^  I  ■       so 


iU    -. 


-T^/ 


Fig.  441.  —  Summer  and  winter  rainfall 
of  India,  the  difference  resulting 
from  the  monsoons. 


Fia.  442.  —  Rainfall  of  northwestern  North  America. 


^a    t43.  —  Subtropical  flora  of  southern  France,  at  Nice,  iu  the  same  latitude 

as  Fortland-  Maine. 


WEATHER  AND  CLIMATE,  285 

CLIMATES  OF   THE   TEMPERATE   ZONES. 

188.    Variation  (in  Temperate  Zones)  from  North  to  South. 

—  (A)  Temperature.  — The  temperature  varies  greatly  from 
near  the  tropics  toward  the  poles ;  but,  excepting  near  the 
tropics,  there  is  everywhere  a  decided  difference  between 
summer  and  winter.  Near  the  polar  circles  the  summers  are 
so  cool,  and  the  winters  so  cold,  that  the  climate  is  often 
called  subarctic.  No  trees  grow  there  (p.  340)  ;  little  or  no 
agriculture  is  possible ;  and  there  are  scarcely  any  human 
inhabitants,  excepting  along  the  seacoast,  or  in  mining  camps, 
like  the  Klondike. 

These  treeless  tundras  merge  into  a  forest  belt,  and  vegeta- 
tion becomes  more  and  more  luxuriant  until,  near  the  tropics, 
the  climate  is  so  warm  that  it  is  called  subtropical.  In  this 
warm  belt  cotton,  sugar,  oranges,  and  even  bananas,  pine- 
apples, and  cocoanuts  are  grown. 

Summary.  —  TJie  climate  of  the  temperate  zones  changes  from, 
cold,  or  subarctic,  near  the  polar  circles  to  hot,  or  subtropical,  near 
the  tropics ;  and  with  these  changes  there  are  variations  in  vegetation 
from  treeless  tundra  to  subtropical  forest. 

(B)  Rainfall. — The  rainfall  also  varies  from  north  to 
south.  Most  temperate  regions  have  a  moderate  rainfall, 
decreasing  toward  the  frigid  zone  and  also  toward  the  trop- 
ics. The  rainfall  decreases  toward  the  frigid  zone,  because 
there  can  be  less  vapor  in  cold  than  in  warm  air  (p.  245). 
It  decreases  toward  the  tropical  zone  because  the  horse  lati- 
tudes are  naturally  arid  regions  (p.  282). 

The  arid  horse-latitude  belts,  in  which  are  included  southern 
California,  southern  Texas,  Spain,  Italy,  Greece,  and  the  steppes 
of  Russia,  grade  in  one  direction  into  the  deserts  of  the  trade- 
wind  belts,  and,  in  the  other,  into  the  damp  climate  of  the  mid- 
temperate  zone.  They  may  be  called  the  belts  of  steppes.  Some 
parts  of  the  horse-latitude  belts,  like  Florida,  have  abundant  rain- 


286  NEW  PHYSICAL   GEOGRAPHY. 

fall,  because  exceptional  conditions  cause  winds  to  blow  from  th^ 
ocean.     Some  parts,  on  the  other  hand,  are  true  desert. 

Steppes  are  dry  in  summer;  but  some  sections  are  reached  by 
the  west  winds  when  they  migrate  southward  in  winter,  bringing 
snow  and  rain.  Therefore  irrigation  is  necessary  for  agriculture, 
as  in  Italy,  which  has  dry  summers  and  rainy  winters.  '  Where 
best  developed,  steppes  are  too  dry  for  trees ;  but  grass  grows  in 
spring,  curing  to  a  natural  hay  during  the  warm,  dry  summer,  thus 
serving  as  a  food  for  cattle. 

Summary. —  The  rainfall  decreases  toward  the  north  because  the 
air  is  cool  ;  in  most  places  it  also  decreases  toward  the  south,  andy 
in  the  horse-latitude  belts,  there  are  regions  of  arid  steppes. 

(C)  Effect  of  Mountains.  —  While  in  southern  Europe  (p.  279) 
subtropical  plants  grow  in  the  latitude  of  the  Kew  England  and 
Middle  Atlantic  States,  in  our  country  such  plants  do  not  thrivSf 
even  in  northern  Florida.  There  are  no  lofty  mountains  to  pre- 
vent cold  north  winds  from  sweeping  down  to  the  Grulf.  There- 
fore cold  waves  reach  as  far  as  New  Orleans  and  northern  Florida., 
causing  frosts  so  destructive  that  it  has  been  necessa,ry  to  give 
up  orange  culture  in  northern  Florida.  In  one  respect  these  cold 
winds  are  an  advantage,  for  they  are  invigorating,  and  the  people 
of  the  South  do  not  suffer,  as  some  warm  temperate  peoples  do, 
:irom  the  enervating  effects  of  too  much  warmth. 

Summary.  —  The  absence  of  east-iuest  mountain  chains  makes  it 
possible  for  cold  ivaves  to  reach  even  to  the  Gulf. 

189.    Variation  (in  Temperate  Zones)  from  Wes"^^  to  East.  — 

Owing  to  the  fact  that  the  prevailing  winds  of  the  temperate 
zones  are  from  the  west,  there  are  decided  differences  in 
climate  from  west  to  east. 

(A)  West  Coasts.  —  The  warm,  damp  winds  that  blow  from 
the  ocean  upon  west-facing  coasts  cause  a  humid,  equable 
climate.  This  is  well  illustrated  on  the  northwest  coast  of 
the  United  States  and  Europe  (pp.  278  and  279).  While 
in  eastern  United  States  droughts  oiten  cause  the  grass 
V)  become  parched,  the  dampness  of  the  air  in  the  Britisli 


WEATHER   AND   CLIMATE.  28 


^ 


Isles  keeps    it   green.     Hence   the   name  Emerald  Isle  for 
Ireland. 

The  heaviest  rainfall  in  the  United  States  is  on  the  north- 
>vest  coast  (Figs.  442,  445),  where  damp  air  from  the  ocean 
Mses  up  the  mountain  slopes.  There  the  rainfall  amounts  to 
100  inches  a  year ;  and  in  winter,  when  the  land  is  cool,  and 
the  westerlies  most  steady,  there  is  rain,  drizzle,  or  fog  almost 
daily.  For  the  'same  reason  there  is  heavy  rainfall  on  the 
southwestern  coast  of  Chile  (Fig.  444).  But  in  the  horse- 
latitude  and  trade-wind  belts,  as  in  southern  California  and 
northern  Chile,  the  climate,  even  on  the  seashore,  is  arid. 

Summary.  —  On  ivest  coasts  of  the  tem2:>erate  zone,  ivhere  reached 
by  the  prevailing  icest  iviiids,  the  climate  is  damp  and  equable.  The 
heaviest  rainfall  in  the  United  States  is  on  the  nortJiivest  coast. 

(B)  Effect  of  JSforth-south  Mountains.  —  Along  the  west 
coast  of  Europe  there  is  especially  heavy  rainfall  on  the 
mountain  slopes,  as  in  Wales,  Scotland,  and  Norway.  But, 
since  these  mountains  are  not  very  high  or  continuous,  the 
winds  are  able  to  carry  vapor  far  inland,  even  into  Asia. 
Because  of  this  fact  Europe,  north  of  the  horse-latitude  belt, 
is  well  watered  and  the  seat  of  extensive  agriculture. 

In  western  North  America,  on  the  other  hand,  as  the  air 
rises  over  the  high,  continuous  mountains,  so  much  of  its 
vapor  is  condensed  that  it  descends  on  their  eastward  slopes 
as  dry  air.  Accordingly,  from  the  Sierra  Nevada-Cascade 
ranges  eastward  to  the  100th  meridian  —  the  part  of  North 
America  which  corresponds  in  position  to  Germany,  Austria, 
and  eastern  Russia  —  most  of  the  country  is  arid ;  and  even 
farther  east,  in  the  Mississippi  valley,  there  are  frequent  and 
destructive  droughts. 

Summary. — Western  United  States  differs  from  Europe  in  the 
greater  influence  of  its  higher,  more  continuous  mountains,  which 
cause  the  winds  that  cross  them  to  reach  the  other  side  dry,  forming 
arid,  regions  as  far  east  as  the  100th  meridian. 


288  NEW  PHYSICAL   GEOGRAPHY. 

(C)  Interior  of  Cojitinents,  —  The  interior  of  a  continent, 
being  far  from  the  sea,  receives  much  less  rainfall  than  a 
windward  coast.  Thus  there  are  frequent  periods  of  drought 
in  central  western  Asia  and  in  central  United  States.  These 
droughts  are  less  destructive  in  the  northern  part,  because  in 
a  cool  climate  lighter  rainfall  suflfices  for  crops.  There  are 
two  reasons  for  this  :  (1)  in  cool  climates  the  slight  evapora- 
tion allows  the  dampness  to  remain  long  in  the  ground ; 
(2)  melting  frost  keeps  the  soil  damp  for  a  long  time. 

One  striking  peculiarity  of  the  interior  of  continents  is 
the  great  range  of  temperature  between  the  warm  or  hot 
summers  and  the  very  cold  winters  (Figs.  431-435).  Dur- 
ing the  summer  day  the  temperature  may  rise  above  100°  — 
truly  tropical  heat ;  and  in  winter  it  may  descend  to  the 
Arctic  cold  of  even  40°  below  zero,  giving  a  range  of  perhaps 
140°  in  a  single  year.  Minnesota  and  neighboring  states  illus- 
trate this  extreme,  or  continental  climate.  It  is  also  illus- 
trated in  central  northern  Siberia,  near  the  Arctic  circle, 
where  moderately  warm  summers  are  followed  by  bitterly 
cold  winters.  In  fact,  this  is  the  coldest  known  place  (Figs. 
431,  435),  and  has  been  called  the  cold  pole  of  the  earth. 

It  is  distance  from  the  sea,  and  freedom  from  its  influence, 
that  account  for  the  extreme  climate  of  the  interior  of  continents. 
The  land  warms  in  summer,  when  the  sun,  though  low  in  the 
heavens,  stays  long  above  the  horizon.  In  winter,  on  the  other 
hand,  the  nights  are  very  long,  and  during  the  short  days  the  sun 
is  low  in  the  heavens.  Under  these  conditions  radiation  is  far  in 
excess  of  the  heat  supplied,  and  the  land  becomes  exceedingly  cold. 

Summary.  — Interiors  of  continents,  being  far  from  the  sea,  are  sub- 
ject to  drought  ;  and  there  is  great  range  in  temperature,  from  icarm  or 
hot  summers  to  cold  winters.     This  is  known  as  a  continental  climate. 

(D)  JEast  Coasts.  —  Since  the  prevailing  westerlies  must 
cross  the  continent  before  reaching  east  coasts,  one  might 
expect  to  find  arid  climates  there.     Aridity  is  prevented, 


2 
o 


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a 

I— i 
f— I 

a 


6 


WEATHER  AND   CLIMATE.  289 

however,  by  the  winds  of  the  cyclonic  storm  eddies  (p.  262), 
which  frequently  replace  the  west  winds.  Some  of  these 
winds  blow  from  the  Atlantic  or  Gulf  of  Mexico,  bringing  the 
vapor  which  gives  eastern  United  States  its  abundant  rainfall. 
Because  of  the  influence  of  cyclonic  storms,  the  climate 
of  east  coasts  is  variable.  The  west  winds  are  dry  and 
cool  in  summer,  and  dry  and  cold  in  winter  ;  but  whenever 
storm  winds  blow  from  the  sea,  both  the  temperature  and 
humidity  are  influenced  by  the  ocean.  Thus  in  northeast- 
ern United  States  the  east  winds  are  damp  and  chilly,  being 
cooled  in  passing  over  the  Labrador  current  ;  and  in  sum- 
mer they  often  bring  fogs.  The  south  winds,  warmed  in 
passing  over  the  Gulf  Stream  or  the  Gulf  of  Mexico,  are 
warm  and  damp.  From  day  to  day  the  weather  varies 
(p.  265),  one  day  being  like  the  interior  of  continents, 
another  like  the  equable  ocean. 

Summary.  —  TJie  cyclonic  storyn  eddies  of  the  ivest-wind  belts  give 
east  coasts  a  very  variable  climate,  ivith  rain  when  winds  bring  abun- 
dant vapor  from  the  sea. 

190. — Variable  Winds  of  the  Prevailing  Westerlies. — Among  the 
winds  caused  by  the  passage  of  cyclonic  storms  and  anticyclones 
(p.  265)  are  some  so  distinctive  that  they  deserve  special  names. 
The  gentle  south  wind,  which  causes  oppressively  warm  weather 
in  summer,  and  unseasonable  warmth  in  winter, maybe  called  the 
sirocco.  It  is  when  the  sirocco  blows  that  thunder  storms  and 
tornadoes  develop  in  summer,  and  thaws  occur  in  winter. 

Of  the  very  opposite  type  are  the  west  and  northwest  winds 
that  sometimes  blow  on  the  rear  of  vigorous  winter  cyclones. 
These  cold  winds,  often  filled  with  snow,  are  called  blizzards  in 
Dakota  and  northers  in  Texas.  Because  of  the  marked  difference 
in  the  barometric  gradient  (p.  255)  between  the  cyclone  and  the 
anticyclone  the  air  moves  with  great  velocity,  perhaps  40  to  60 
miles  an  hour.  The  cold,  and  the  fierce  snow  squalls,  often  cause 
destruction  of  life  among  sheep  and  cattle ;  even  men  are  some- 
times lost  in  the  blinding  snow,  and  frozen  by  the  fierce  cold. 
Milder  forms  of  blizzard  occur  in  northeastern  United  States. 


290 


NEW  PHYSICAL   GEOGRAPHY. 


A  cold  ivave  (Fig.  446)  is  a  rapid  drop  in  temperature  during 
the  passage  of  a  well-developed  anticyclone  (p.  263).  At  such 
times  a  wave  of  cold  air  spreads  over  a  large  part  of  the  country, 
even  down  to  the  Gulf  (p.  286).  This  blanket  of  air  descends 
from  the  cold  northern  interior  and  from  aloft  (Fig.  417) ;  and 
since  it  is,  therefore,  warming  as  it  spreads  out,  it  is  clear  and 
dry.  Through  it  radiation  proceeds  readily,  causing  very  low 
temperatures  in  winter,  refreshingly  cool  weather  in  summer,  and 
early  and  late  frosts  in  fall  and  spring  (p.  246).  The  term  cold 
wave,  however,  is  commonly  applied  only  to  the  winter  condition. 


120  jlO^es-.    !!*>' 


Fia.  446.—  A  cold  wave,  spreading  outward  from  an  area  of  high  pressure  in  the 
northwest,  November  27,  1896.    Arrows  show  outward  movement  of  the  air. 


The  passage  of  cyclonic  storms  sometimes  causes  an  exceed- 
ingly warm,  dry  wind,  known  as  the  foehn  in  the  Alps  and  the 
Chinook  in  the  Rocky  Mountains.  These  winds  are  caused  by  the 
rapid  passage  of  air  across  mountains  toward  a  storm  center.  As 
the  air  rises  on  one  side  it  loses  much  of  its  vapor,  descending  as 
dry  air  on  the  opposite  side.  It  descends  so  rapidly  that  it  is 
warmed  by  compression,  as  the  air  in  a  bicycle  pump  is  warmed 


WEATHER  AND   CLIMATE.  291 

(p.  241).  This  warming  lowers  the  relative  humidity  (p.  244)  un- 
til the  air  becomes  very  dry ;  in  fact,  the  Swiss  formerly  believed 
that  the  foehn  came  from  the  Sahara.  In  the  warm,  dry  air,  snow 
disappears  rapidly,  and  houses  become  so  dry  that  fires  are  greatly 
feared.  Whole  villages  in  Switzerland  have  been  wiped  out  by 
fire  during  the  foehn  winds. 

Summary. — A  sirocco  is  a  ivarm,  gentle  south  wind  blowing 
tovmrd  a  cyclonic  storm  ;  a  blizzard,  or  norther,  is  a  fierce,  cold  wind, 
ivith  squalls  of  snow,  in  the  area  between  yjell-defined  cyclones  and 
anticylones ;  a  cold  ivave  is  the  outspreadiyig  blanket  of  cold 
air  in  an  anticyclone ;  the  foehn,  or  chinook,  is  a  ivarm,  dry  moun- 
tain wind  made  ivarm  and  dry  by  rapidly  descending  the  mountain 
slopes  in  its  passage  toward  a  low  pressure  area. 

191.  Weather  of  Eastern  United  States.  —  (A)  Summer 
Weather.  —  The  typical  summer  weather  of  eastern  United 
States  may  be  illustrated  by  the  following  actual  instance. 
A  cool,  dry,  gentle  west  wind  is  accompanied  by  a  day  of 
agreeable  warmth,  a  night  of  refreshing  coolness,  and  a 
nearly  cloudless  sky.  An  anticyclone  is  passing  over  the 
region,  and  following  it  is  an  area  of  moderately  low  pres- 
sure. As  this  approaches,  the  wind  veers  to  the  southeast, 
the  temperature  rises,  the  air  becomes  more  humid,  and  both 
day  and  night  are  muggy  and  oppressive.  On  the  morning 
of  the  second  day,  clouds  fleck  the  sky,  in  the  afternoon 
growing  to  thunder-heads.  About  four  o'clock  a  thunder 
storm  appears,  preceded  by  a  fierce  squall  ;  then  comes  heavy 
rain,  accompanied  by  vivid  lightning  and  crashing  thunder. 
After  the  storm,  a  west  wind  blows  and,  as  another  anti- 
cylone  passes,  the  air  is  again  dry  and  refreshing. 

This  cycle  is  repeated  with  some  regularity,  though  there  are 
numerous  variations..  At  times  the  low  pressure  areas  are  so 
poorly  developed  that  for  several  weeks  little  rain  falls.  There 
is  then  a  drought,  during  which  streams  and  wells  run  dry,  vege- 
tation withers,  and  crops  suffer.  At  other  times  a  low  pressure 
area  is  so  well  developed  that,  instead  of  scattered  thunder  storms, 


292 


NEW  PHYSICAL   GEOGRAPHY. 


there  is  general  cloudiness  and  rain.  This  is  especially  true  in 
late  summer  and  early  autumn,  when  hurricanes,  accompanied  by 
strong  winds  and  heavy  rains,  pass  up  the  coast. 

Summary. — Summer  weather  in  eastern  United  States  is  vari- 
able, being  warm  and  oppressive,  often  with  thunder  storms,  ivhen 
south  winds  blow  toward  moderately  developed  areas  of  low  pressure, 
and  cool  and  refreshing  when  anticyclones  pass. 

(B)  Winter  Weather  (Figs.  446-453). — Both  cyclones  and 
anticyclones  are  much  better  developed  in  winter  than  in  sum- 
mer. They  pass 
over  the  country 
in  fairly  regular 
succession  (p.  263), 
bringing  alternate 
clear  and  cloudy 
weather.  Their 
ap[)earance  is  some- 
times so  regular 
that  one  day  of 
the  we  e  k  has 
nearly  the  same 
kind  of  weather 
for  several  succes- 
sive weeks. 

During  the  pas- 
sage of  cyclones 
there  may  be  rain, 
or  snow,  or  both. 
The  wind  varies  in 
velocity  (p.  265)  and  veers  through  various  quarters,  bring- 
ing chilly  air  from  the  north  or  east,  warm  air  from  the  south. 
While  the  south  wind  is  blowing  a  thaw  may  set  in,  and,  even 
in  midwinter,  rain  may  fall  as  far  north  as  Canada.  A  thaw 
is  often  followed  by  a  decided  drop  in  temperature  as  the 
next  anticyclone  approaches. 


,\e\gy 


Fig.  447. — A  winter  storm,  showing  winds  blowing 
toward  a  Low,  and  the  large  area  over  which  rain 
(dotted)  and  snow  (cross-lined)  are  falling. 


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WEATHER   AND   CLIMATE,  293 

Few  climates  of  the  world  are  so  variable  as  these  of  the  stormy 
west-wind  belts ;  and  the  changes  in  weather  are  very  trying  to 
the  health.  Consequently  many  diseases,  such  as  pneumonia, 
grippe,  and  consumption,  are  common  in  these  severe  climates. 

Summary.  —  The  winter  weather  of  the  west-wind  belts  is  exceed- 
ingly variable,  being  cold  daring  the  2Jassage  of  anticyclones,  and  rela- 
tively ivarm  during  the  i^assage  of  cyclonic  storms,  whose  south  winds 
may  even  cause  midicinter  thaics. 

192.  Climate  of  the  South  Temperate  Zone.  —  Owing  to  the  fact 
that  there  is  so  much  water  in  the  southern  hemisphere,  the 
changes  in  temperature  are  less  extreme  there  than  in  the  northern 
hemisphere  (Fig.  435)  ;  and  the  winds  blow  with  more  strength  and 
steadiness  than  over  the  irregular  lands  (p.  261).  Otherwise  the 
climates  of  the  two  temperate  zones  are  much  alike.  Over  the 
Southern  Ocean  the  summer  weather  is  damp  and  chilly,  the  winter 
raw  and  cold,  though  without  extreme  changes  from  warm  to  ex- 
ceedingly cold  weather.  Storms  are  frequent  and  fierce,  and  this 
is  why  rounding  Cape  Horn  is  so  dreaded  by  sailors. 

Summary.  —  Excepting  for  stronger,  steadier  winds,  more  uniform 
coolness,  and  less  decided  changes  in  temperature,  the  climate  of  the 
south  temperate  zone  is  similar  to  that  of  the  north  temperate. 

193.  Arctic  Climates.  —  (A)  Near  the  Circle.  —  In  summer, 
when  the  sun  is  above  the  horizon  both  day  and  night,  the 
air,  though  cool  and  sometimes  raw,  is  never  very  cold.  The 
warmth  melts  the  frost  to  a  depth  of  two  or  three  feet, 
making  the  soil  damp  and  swampy.  Then  the  grass  becomes 
green,  flowers  blossom,  and  birds  and  insects  appear.  ~  As  in 
other  places  visited  by  the  westerlies,  storms  appear  in  fairly 
regular  succession,  bringing  rain  or  squalls  of  snow.  Fogs 
are  common  on  the  sea  and  along  the  coast,  where  damp 
winds  are  chilled  in  passing  over  cold  water. 

In  the  late  summer,  when  the  sun  commences  to  set,  the 
days  grow  cooler  and  the  nights  cold.  Insects  disappear, 
birds  move  southward,  and  the  land  is  covered  with  snow. 


294  NEW  PHYSICAL   GEOGRAPHY. 

The  soil  freezes  again,  and  a  skim  of  ice  appears  on  the 
ocean,  growing  thicker  as  the  days  become  shorter.  The 
Eskimo  then  gives  up  his  kayak  and  takes  to  the  sledge  in 
search  of  seal,  liis  chief  food.  Finally  the  sun  is  absent 
even  at  noon,  and  then  the  weather,  both  day  and  night,  is 
bitterly  cold.  In  winter  the  principal  changes  are  those 
accompanying  tlie  passage  of  cyclonic  storms.  Sometimes, 
even  in  midwinter,  the  temperature  rises  so  high  that  the 
Eskimo  snow  houses,  or  igloos  (Fig.  525),  begin  to  melt. 

With  the  coming  of  spring  the  sun  reappears,  the  snow 
melts,  and  the  Eskimo  abandons  his  igloo  for  a  skin  tent,  or 
tupic  (Fig.  524).  The  sea  ice  begins  to  break  up  and  float 
away,  and  the  Eskimo  returns  to  his  kayak  for  hunting. 
Then  comes  the  summer  day. 

Summary. —  The  Arctic  summer,  near  the  Circle,  is  cool,  damp,  and 
stormy.  In  lointer,  ivhen  the  sun  is  beloiv  the  horizon  even  at  mid- 
day, the  ground  is  frozen  and  snow-covered,  the  sea  covered  with  ice, 
and  the  weather  bitterly  cold. 

(B)  Nearer  the  Pole.  —  As  near  the  pole  as  man  has  gone  the 
climate  has  been  found  similar  to  that  just  described  ;  but  the 
Arctic  winter  night  is  longer  and  colder,  the  summer  cooler. 
Even  there  the  warmth  of  the  summer  sun  is  sufficient  to  remove 
the  snow  from  much  of  the  low  ground  near  the  coast.  In  up- 
per Greenland,  the  northernmost  land  known,  and  far  north  of 
the  highest  Eskimo  settlements,  Peary  found  flowers  blossoming, 
insects  humming,  and  musk  oxen  roaming  about  in  summer. 

The  sea  which  surrounds  the  North  Pole  is  everywhere  covered 
with  ice  floes  (p.  194),  over  which  Abruzzi,  Nansen,  Peary,  and 
others  have  tried  to  reach  the  pole.  They  must  make  their  dash 
in  early  spring,  because  in  summer  the  ice  is  too  broken  to  cross 
on  sledges,  yet  not  open  enough  to  allow  ships  to  pass  through. 
Consequently  those  who  have  tried  to  reach  the  pole  have  gone  as 
far  north  as  ships  will  carry  them,  and  remained  through  the  cold, 
dreary  Arctic  night  in  order  to  be  ready  for  an  early  start.  At 
last  Peary  overcame  the  difficulties  of  ice  and  climate  that  had  so 
long  baffled  explorers,  and  in  April,  1909,  reached  the  North  Pole. 


WEATHER   AND   CLIMATE.  295 

Summary.  —  As  far  north  as  man  has  gone,  the  climate  is  similar 
to  that  Clearer  the  Arctic  Circle,  though  coolei-  in  summer  and  colder 
in  winter,  because  the  sun  is  lower  and  longer  below  the  horizon. 
Plants  and  animcds  live  on  the  northmost  known  land.  In  summer 
the  sea  ice  breaks  up  so  that  travel  over  it  by  sledge  is  impossible. 

Topical  Outline,  Questions,  and  Suggestions. 

Topical  Outline.  — 181.   Difference  between  Weather  and  Climate.  — 

Weather  ;  climate  ;  illustration  of  difference  ;  kinds  of  climate. 

182.  Zones  of  heat. —'(A)  The  Five  Zones:  reason  for  division  ;  the 
zones;  boundaries.  (B)  Influence  of  Altitude:  effect  of  highlands; 
isotherms;  isothermal  charts;  Pacific  slope.  (C)  Influence  of  Water: 
contrast  ocean  and  land ;  illustrations  ;  temperature  ranges.  (D)  Influ- 
ence of  Winds  :  contrast  western  Europe  and  eastern  United  States  ;  east- 
ern and  western  United  States.  (E)  Influence  of  Ocean  Currents :  effect 
on  winds ;  transference  to  land ;  contrast  western  Europe  and  eastern 
America.  (F)  Influence  of  Topography :  local  influences ;  mountain 
barriers ;  western  United  States  ;  Mediterranean. 

183.  Belt  of  Calms. — Warmth;  rain;  weather  on  the  ocean;  on 
the  land;  forests;  mankind. 

181.  Rainy  Trade-wind  Belts.  —  Effect  of  warming  air;  evaporation 
of  sea  water;  east-facing  coasts;  instances;  forests;  Hawaiian  Islands. 

185.  Desert  Trade-wind  Belts.  —  Explanation  ;  rainfall ;  desert  belts ; 
horse-latitude  arid  climate;  desert  life;  weather  conditions. 

186.  Savanna  Belts.  —  Location  ;  cause  of  peculiar  climate  ;  effect  on 
vegetation;  instances  of  savannas ;  animals;  man. 

187.  The  Indian  Climate.  —  Hot,  windy  season ;  hot,  calm  season ; 
the  rains ;  short,  hot  period ;  winter  monsoon ;  effect  of  these  changes 
on  vegetation  ;  heavy  rains  at  base  of  Himalayas. 

188.  Variation  (in  Temperate  Zones)  from  North  to  South.  —  (A)  Tem- 
perature ':  near  polar  circles ;  near  tropics  ;  vegetation.  (B)  Rainfall :  in 
the  north;  in  the  south;  steppes.  (C)  Effect  of  Mountains :  Contrast 
southern  Europe  and  United  States ;  effect  on  people. 

189.  Variation  (in  Temperate  Zones)  from  West  to  East. —  (A)  West 
Coasts :  climate  of  west  coasts ;  contrast  British  Isles  and  eastern 
United  States ;  rainfall  of  western  United  States ;  Chile.  (B)  Effect  of 
North-south  Mountains  :  western  Europe ;  interior  of  Europe  ;  western 
United  States;  country  east  of  mountains.  (C)  Interior  of  Continents: 
rainfall;  droughts ;  the  cool  north  ;  great  temperature  range  ;  continental 
climate;  instances;  explanation.  (D)  East  Coasts:  effect  of  storms  on 
rainfall ;  in  causing  variable  climate ;  changes  from  day  to  day. 


296  NEW  PHYSICAL   GEOGRAPHY. 

190.  Variable  Winds  of  the  Prevailing  Westerlies.  ^  (a)  Sirocco 
nature ;  cause  ;  effects,  (h)  Blizzards  or  northers :  location ;  reason  for 
strong  winds;  effects,  (c)  Cold  waves:  nature;  location;  cause  of 
cold;  effects,  (d)  Foehn  or  chinook :  location;  cause  of  warmth; 
cause  of  dryness ;  effects. 

191.  Weather  of  Eastern  United  States.—  (A)  Summer  Weather:  (a)  typ- 
ical cycle:  anticyclone;  warm  south  winds;  thunder  storms;  anticy- 
clone. (6)  Variations  from  cycle :  droughts ;  general  rain.  (B)  Winter 
Weather :  regular  succession  of  cyclones  and  anticyclones  ;  precipitation ; 
wind  changes;  thaws;  effect  of  changes  on  health. 

192.  Climate  of  the  South  Temperate  Zone.  —  Effect  of  water  on  tem- 
perature ;  on  winds ;  summer  weather ;  winter  weather ;  storms. 

193.  Arctic  Climates. —  (A)  Near  the  Circle:  summer  climate;  plants 
and  animals;  storms;  fog;  change  in  autumn;  effect  on  life;  winter  cli- 
mate ;  effect  on  Eskimos  ;  spring  climate  ;  effect  on  Eskimos.  (B)  Nearer 
the  Pole :  resemblance  to  conditions  farther  south  ;  differences ;  life ;  sea 
ice;  time  of  making  dash  toward  the  pole. 

Questions.  — 181.  What  is  weather?  Climate?  Illustrate  the 
difference.     Name  some  different  kinds  of  climate. 

182.  (A)  Why  may  the  earth  be  divided  into  zones  of  heat?  What 
about  the  boundaries  ?  (B)  What  is  the  influence  of  highlands?  What 
is  an  isotherm?  An  isothermal  chart?  What  is  the  condition  on  the 
Pacific  slope?  (C)  What  differences  are  there  over  land  and  water? 
Give  illustrations.  (D)  Give  illustrations  of  the  influence  of  winds  on 
climate.  (E)  How  do  ocean  currents  affect  climate  ?  Give  instances. 
(F)  What  effect  has  topography  on  climate  ?     Give  instances. 

183.  What  is  the  climate  of  the  belt  of  calms  ?  What  is  the  weather 
on  the  ocean?     On  the  land?     What  effect  has  the  climate  on  man? 

184.  What  effect  have  the  trade  winds  on  the  sea?     On  rising  coasts? 

185.  Why  are  there  deserts  in  the  trade-wind  belts  ?  Where  are  the 
great  desert  belts?  Why  are  the  horse  latitudes  arid?  What  are  the 
life  conditions  in  the  desert?     What  are  the  weather  conditions? 

186.  What  is  the  cause  of  the  savannas?  What  are  the  conditions 
there.     What  effect  have  these  conditions  on  life? 

187.  Describe  the  Indian  climate:  the  seasons;  their  cause;  their 
effect  on  vegetation  ;  the  heavy  rains. 

188.  (A)  What  are  the  conditions  near  the  polar  circle?  IIow  do 
tlie  temperature  and  vegetation  change  toward  the  tropics?  (B)  How 
does  the  rainfall  vary  from  north  to  south?  What  are  steppes?  Where 
found?  What  are  the  conditions  there?  (C)  What  is  the  result  of  the 
absence  of  lofty  mountains  in  southern  United  States? 

189.  Why   are    there   differences   "m    climate    from    west  to    east'/ 


WEATHER  AND   CLIMATE,  297 

(A)  What  is  the  climate  of  west-facing  coasts?  Why?  Give  illus- 
trations. (B)  Contrast  central  Europe  with  the  arid  West.  Explain  the 
condition  in  the  United  States.  (C)  What  is  the  condition  of  rainfall  in 
the  interior?  Why  are  droughts  less  destructive  in  the  north?  What 
are  the  temperature  conditions?  Why?  (D)  What  is  the  cause  for 
rainfall  on  east-facing  coasts?     How  does  the  climate  vary?     Why? 

190.  What  is  the  sirocco?  The  norther?  The  blizzard?  What  is 
the  cause  of  each?  Their  effect?  What  is  the  c^Aise  of  cold  waves? 
Explain  the  foehn  or  the  chinook  wind.     What  are  their  effects? 

191.  (A)  Describe  a  cycle  of  typical  summer  weather  in  eastern  United 
States.  What  causes  variations  from  this  cycle?  (B)  Describe  the  win 
ter  weather.     What  causes  thaws?     What  is  the  effect  of  the  changes? 

192.  How  does  the  climate  of  the  south  temperate  zone  differ  from 
that  of  the  north  ? 

193.  (A)  Describe  the  Arctic  climate  in  the  different  seasons.  How 
do  these  changes  influence  life?  (B)  What  is  the  condition  of  climate 
nearer  the  pole  ?     Why  is  it  so  difficult  to  reach  the  pole  ? 

Suggestions.  —  (1)  Trace  one  or  two  of  the  isothermal  lines  across 
the  charts  for  the  United  States  (Figs.  433,  434)  and  endeavor  to  explain 
the  irregularities.  Do  the  same  for  one  or  two  isotherms  in  the  north- 
ern hemisphere  of  the  world  charts  (Figs.  431,  432).  Follow  one  or 
two  in  the  southern  hemisphere  and  account  for  the  difference  between 
their  regularity  and  the  irregularity  of  those  in  the  northern  hemisphere. 
(2)  Make  isothermal  charts  of  the  United  States  and  the  world,  copying^ 
upon  outline  maps  the  isotherms  in  the  book.  (3)  Study  the  Appen- 
dix on  weather  maps  (Appendix  H)  and  work  out  the  suggestions. 
(4)  Select  and  study  weather  maps  illustrating  cold  waves.  (5)  From 
a  series  of  three  weather  maps  for  successive  days,  describe  the  weather 
changes  at  a  given  place  —  say  Boston  or  Chicago.  Write  down  the 
temperature,  wind  direction,  etc.,  for  each  of  the  days.  (6)  Make  a 
record  of  local  weather  changes  for  a  week.  Write  a  short  description  of 
these  changes.     (7)  Write  a  description  of  the  climate  of  your  home. 

Reference  Books.  —  Ward,  Hann's  Handbook  of  Climatology,  Mac- 
millan  Co.,  New  York,  1903,  ^3.00;  Greely,  American  Weather,  Dodd, 
Mead  &  Co.,  New  York,  1888,  $2.50;  Turner,  Climate  of  New  York  Siate, 
Chapter  XI,  Physical  Geography  of  New  York  State,  Macmillan  Co'.  New 
York,  1902,  ^3.50;  Croll,  Climate  and  Tme,  Appleton  &  Co.,  New  \  :>r'x, 
1 890,  $2.50.     (See  also  references  at  end  of  Chapter  XII.) 


CHAPTER  XV. 

PHYSIOGRAPHY  OF  THE  UNITED  STATES. 

The  United  States  illustrates  in  many  ways  the  effect 
of  physiographic  conditions  on  the  industries  and  develop- 
ment of  the  various  sections.  In  previous  chapters  reference 
has  frequently  been  made  to  these  influences.  These  refer- 
ences, with  others  added,  are  summarized  in  this  chapter. 

194.  New  England.  —  New  England  is  a  region  of  very 
ancient  mountains  of  hard  rock,  including  crystalline  gneisses, 
schists,  and  granites.  These  strata  are  complexh^  folded, 
and  worn  by  denudation  to  the  condition  of  hills  and  low 
mountains  (Fig.  460).  It  is  held  by  many  that  this  region 
was  worn  down  to  a  peneplain  (Fig.  171),  with  here  and 
there  a  peak,  or  group  of  peaks,  rising  above  the  general 
level.  Such  peaks  have  been  called  monadnocks,  after  Mt. 
Monadnock,  N.H.  (Fig.  455),  which  rises  well  above  the 
fairly  uniform  sky  line  of  the  surrounding  hilltops. 

After  the  mountains  were  reduced  to  a  low  hilly  condi- 
tion, there  was  an  uplift  of  the  land,  which  permitted  the 
streams  to  sink  their  valleys  into  the  ancient  mountains. 
This  occurred  so  long  ago  that,  even  in  the  resistant  rocks,  the 
valleys  have  been  broadened  to  the  condition  of  early  matu^'- 
ity.  The  Connecticut  valley,  in  weaker  sandstones  ai,i 
shales,  has  been  broadened  to  a  wide  lowland  (Fig.  86),  witn 
here  and  there  liills  of  more  resistant  trap  rock,  like  Mts 
Tom  (Fig.  229)  and  Holyoke,  rising  above  tlie  valley  fioor, 

Tliere  is  little  mineral  wealth  in  New  England,  witli  tlie 
exception    of   abundant   building  stone,   including   granite, 

298 


FHYSIOGRAPHY  OF  UNITED   STATES,  299 

slate,  and  marble,  which  finds  a  market  in  many  parts  of 
the  country.  There  is  hardly  any  coal,  and  very  little  iron 
or  other  metals. 

Over  all  this  region  the  ice  sheet  spread,  rounding  the 
hills  and  deepening  some  of  the  valleys.  The  residual  soil 
was  swept  away,  and  in  places,  especially  on  steep  slopes,  the 
rock  was  left  bare;  but  usually  it  was  covei^ed  by  a  glacial 
soil.  This  soil  varies  greatly  from  sterile  to  fertile,  from 
thin  to  thick,  and  from  clayey  to  bowldery  (Figs.  284,  285). 
Over  a  large  part  of  New  EngUtnd  the  glacial  soil  is  too 
thin,  or  too  sandy,  or  too  rocky,  for  cultivation. 

Because  of  the  hilly  nature  of  the  land,  the  many  steep 
slopes,  and  the  poor  soil,  New  England  is  not  a  good  farming 
country.  In  fact,  the  forest  has  been  allowed  to  remain  on 
large  areas  (Fig.  189) ;  and,  for  this  reason,  the  more  moun- 
tainous northern  and  western  parts  are  among  the  important 
forest  regions  of  the  country.  Under  such  conditions  the 
farms  are  necessarily  small  (Fig.  457),  and  the  area  suited 
to  farming  is  not  nearly  large  enough  to  supply  the  needs  of 
the  busy  manufacturing  towns  and  cities.  The  great  food 
staples,  such  as  wheat,  arejbrought  from  the  West,  while  New 
England  farms  are  devoted  mainly  to  the  production  of  vege- 
tables, dairy,  and  similar  products  for  neighboring  towns. 

The  glacial  deposits  have  formed  many  lakes  and  turned 
aside  many  streams,  which  now  tumble  in  rapids  and  falls 
over  ledges  which  they  have  discovered.  Hundreds  of  cities 
and  towns  use  this  water  power  for  manufacturing,  which 
stands  at  the  foundation  of  New  England's  prosperity.  The 
lakes  aid  in  regulating  the  water  supply. 

During  the  glacial  period  the  land  sank  and  the  sea  entered 
the  valleys,  forming  a  very  irregular  coast  line  (Figs.  388, 
389),  with  many  bays  and  good  harbors.  This  irregular  coast 
line  is  favorable  to  fishing,  one  of  the  most  important  indus- 
tries of  New  England;  and  it  earb^  encouraged  sliip  building, 
for  which  the  forests  supplied  the  lumber.     The  beautifu' 


300 


NEW  PHYSICAL   GEOGRAPHY, 


scenery  of  this  irregular  coast,  and  the  cool  climate,  attract 
many  people  in  summer. 

The  many  harbors  have  encouraged  navigation.  This 
navigation  aids  manufacturing  by  furnishing  a  means  of 
bringing  raw  materials  and  of  removing  manufactured  arti- 
cles to  places  where  they  are  used.  Though  irregular,  the 
coast  is  low  enough  to  permit  the  easy  construction  of  rail- 
ways; and  the  broad,  mature  valleys  of  the  interior  are  also 
easily  traversed  by  them.  Consequently,  railway  lines 
radiate  from  the  leading  ports  to  cities  both  inland  and 
along  the  coast.  In  this  respect  New  England  differs 
greatly  from  mountainous  Norway,  where  communication 
between  points  along  the  irregular  coast  must  be  by  boat. 

Many  of  the  busy  manufacturing  cities  of  New  England 
(Fig.  456),  such  as  Providence,  Fall  River,  New  Bedford, 

New  Haven,  Bridgeport,  and 
Portland,  are  on  the  sea. 
Others,  like  Worcester,  Lowell, 
Lawrence,  '  Hartford,  and 
Springfield,  are  in  the  inte- 
rior, generally  near  water 
power.  By  far  the  largest  city 
is  Boston,  on  the  sea.  Its 
growth  depends  upon  a  num- 
ber of  favorable  circumstances. 
It  is  in  a  central  position,  on 
that  part  of  the  coast  which 
extends  farthest  into  the  inte- 
rior of  New  England,  and  it  has  an  excellent  harbor.  Com- 
munication along  the  coast  is  possible  by  rail  and  boat;  the 
interior  is  easily  accessible  by  rail;  and  all  parts  of  the 
world  are  open  to  its  commerce.  All  eastern  Massachusetts 
is  tributary  to  this  port,  which  lies  in  the  center  of  a  semi- 
circle of  manufacturing  towns  (Fig.  454),  one  of  the  busiest 
manufacturing  regions  of  the  world. 


Fig.  454.—  To  show  the  location  of 
Boston  with  the  ring  of  surround- 
ing towns  and  cities. 


ipy/..!ti»iai)jmiini  1 1  will 


■mfM-'<|Pjgi.l.»'.IM^  liMWIipj  ■^^  ■  nii>  Jj.iiii,  n.j»>wij»{y»regWf|pH|ipyPBpg|g| 


Fig.  455. — Mt.  Monadnock,  rising  above  the  general  level  of  the  upland  of 

southern  New  Hampshire. 


Fig.  456.  —Distribution  of  towns  and  cities  in  New  England. 


PHYSIOGRAPHY  OF  UNITED  STATES.  301 

In  its  physical  geography,  ISTew  England  resembles  parts  of 
Great  Britain  and  Scandinavia.  In  each  case  the  coast  is  irregu- 
lar, the  land  hilly,  and  much  of  the  soil  poor.  Scandinavia,  like 
the  more  hilly  part  of  New  England,  has  a  large  proportion  of  its 
area  uncleared  of  forest.  It  is  more  mountainous  than  most  of 
New  England,  and  has  little  manufacturing ;  but  its  irregular 
coast  has  encouraged  the  development  of  fishing  and  shipping. 
Great  Britain  pays  far  more  attention  to  manufacturing  than  to 
agriculture,  and,  like  New  England,  depends  upon  other  sections 
for  a  large  part  of  its  supply  of  food  and  raw  materials. 

Summary.  —  Neic  England  is  a  region  of  ivorn-doicn,  ancient 
mountains,  with  hilltops  rising  to  a  fairly  even  sky  line,  but  with 
peaks  and  groups  of  peaks  rising  above  this  level,  especially  in  the 
vjest  and  north.  Many  of  these  are  still  forest-covered.  Tlie  valleys 
are  fairlv  broad,  even  in  the  hard  rock,  favoring  the  construction  of 
roads  ai»^l  railways.  The  ice  sheet  has  left  a  glacial  soil,  tvhich, 
together  with  the  hilly  condition,  makes  this  a  poor  farming  region. 
There  is  little  miner-al  wealth,  excepiting  building  stone.  In  spite  of 
the  genercd  absence  of  raw  products,  the  icater  power,  due  to  glacial 
interference  with  streams,  has  encouraged  the  development  of  manu- 
facturing;  and  this  has  been  further  aided  oy  the  irregular  coast, 
caused  by  sinking  of  the  land.  TJiis  irregular  coast  is  favorable  to 
fishing  and  to  navigation.  Of  the  many  manufacturing  cities  Bos- 
ton is  most  favorably  situated  and  is,  therefore,  the  largest. 

195.  New  York.  —  The  physiography  of  the  Empire  State 
is  more  varied  than  that  of  New  England.  New  York  may 
be  divided  into  four  quite  different  regions:  (1)  the  Adi- 
rondacks,  resembling  the  more  mountainous  parts  of  New 
England;  (2)  the  low,  hilly  region  of  southeastern  New 
York,  which  resembles  southwestern  New  England;  (3)  the 
high,  hilly  plateau,  including  the  Catskills  and  southern  and 
western  New  York;  and  (4)  the  plains  which  border  Lakes 
Erie  and  Ontario.  The  ice  sheet  covered  the  entire  state, 
excepting  the  extreme  southwestern  corner  (Fig.  270). 
Therefore,  in  various  parts  of  the  state,  there  are  moraines 
(Figs.  273,  274),  wash  plains   (Fig.    275),  drumlins   (Fig. 


302  NEW  PHYSICAL   GEOGRAPHY. 

287),  and  other  glacial  deposits,  and  gorges,  waterfalls  (Figs. 
61,  67,  71,  75),  rapids,  and  lakes. 

The  basis  for  the  great  growth  of  New  York  is  agriculture, 
in  which  it  ranks  high  among  the  states  of  the  Union.  In 
mineral  wealth  the  state  is  not  especially  rich,  though  build- 
ing stone,  clay,  and  salt  are  found  in  excess  of  local  needs. 
There  is  also  some  iron,  oil,  and  gas,  but  no  coal.  However, 
^he  oil,  gas,  and  coal  of  Pennsylvania  are  readily  accessible; 
^ud  the  iron  of  the  Lake  Superior  region  is  easily  brought 
Uy  water  to  Buffalo.  Hence,  manufacturing  cities  have  de- 
veloped wherever  facilities  for  transportation  favored  their 
development.  Water  power,  due  to  glacial  action,  has  also 
"ided  in  the  growth  of  many  towns  and  cities. 

The  Adirondacks,  like  the  higher  parts  of  New  England,  are 
rugged,  mountainous,  rocky,  and  forest-covered  (Fig.  188).  Water 
power  is  used  in  a  series  of  towns  around  their  base,  partly  in 
manufacturing  the  products  of  the  forest,  as  in  making  paper 
from  wood  pulp.  There  are  some  mineral  resources,  including 
iron ;  but  distance  from  lines  of  water  transportation  renders  the 
stores  of  building  stone,  and  most  other  mineral  products,  of  little 
present  use.  As  in  New  England,  these  beautiful  mountains  (Fig. 
299)  are  much  resorted  to  by  sportsmen  and  summer  visitors. 

The  uplands  of  the  Catskills,  and  the  hilly  plateau  of  the 
south  and  west  (Figs.  145,  465),  have  a  thin  and  often  stony  soil. 
This  plateau  is,  therefore,  sparsely  settled,  and  there  are  large 
areas  that  are  stiil  forest-covered.  The  valleys,  being  more  level, 
and  having  thicker  and  better  soil,  are  dotted  with  farms  and 
country  villages.  The  abundance  of  creameries,  for  the  manufac- 
ture of  butter  and  cheese,  shows  that  much  of  this  region  is  better 
adapted  to  pasturage  than  to  grain  and  other  crops. 

The  hills  are  so  difficult  to  cross,  and  so  sparsely  settled,  that 
railways  are  found  mainly  in  the  larger  valleys;  and  it  is  often  a 
long,  roundabout  railway  journey  from  one  valley  to  the  next. 
The  towns  and  cities,  such  as  Binghamton  and  Elmira,  are  in 
the  larger  valleys,  usually  at  points  where  railways  from  tributary 
valleys  enter,  making  these  places  railway  junctions. 


PHYSIOGRAPHY  OP  UNITED  STATES. 


303 


The  level  plains  along  the  shores  of  the  Great  Lakes 
have  a  deep  soil,  deposited  by  the  glacier  and  in  the 
glacial  lakes  (p.  149).  These  lake-shore  plains  are  among 
the  best  farming  lands  of  the  East,  and  the  influence  of  the 
lake  water  gives  them  a  climate  especially  suited  to  fruit 
culture  (p.  166).  From  near  Buffalo  to  Home,  the  Erie  Canal 
(Fig.  458)  crosses  these  plains.  Its  route  is  now  followed 
by  railways  ;  and  the  excellent  facilities  for  transportation 
have  encouraged 
the  growth  of  nu- 
merous towns  and 
cities,  including 
Rochester,  —  at 
the  falls  of  the 
Genesee,  —  Syra- 
cuse, Utica,  Troy, 
and  Albany. 

Numerous  Droad, 
mature  valleys  lead 
back  into  the  pla- 
teau, and  in  some  of 
them  are  large  lakes, 
such  as  Cayuga  (Fig. 
298)  and  Seneca, 
which     have     been 

caused  by  ice  erosion  and  dams  of  glacial  drift.  These  valleys 
and  lakes  afford  opportunities  for  communication  by  water,  road, 
and  railway  with  the  heart  of  the  plateau  country.  In  early  days 
the  Erie  Canal  was  the  only  great  artery  connecting  this  interior 
with  the  sea  ;  but  railways  are  now  added  to  the  canal  to  accom- 
modate the  steady  stream  of  trade,  between  the  West,  the  interior 
of  the  state,  and  the  sea. 

The  movement  of  goods  along  this  route,  which  has  aided 
in  the  growth  of  many  towns  and  cities,  has  especially 
favored  the  cities  at  the  two  ends  —  New  York,  on  the  sea^ 


Fig.  458.  —  Erie  Canal  route. 


304 


NEW  PHYSICAL   GEOGRAPHY, 


l;:;;VWest-t't 
■.•.■?"?.>:e>s^;:-., 
<^:::::::y:'.^'iii' 


and  Buffalo,  on  Lake  Erie.  The  unloading  of  goods  at 
Buffalo  and  New  York,  for  further  shipment,  accounts  in 
part  for  their  growth.  They  are,  moreover,  supplied  with 
abundant  raw  material  for  manufacture  and  have,  therefore, 
become  great  centers  of  manufacturing  and  of  commerce. 

By  reason  of  its 
very  favorable  physi- 
ographic situation 
New  York  has  become 
the  largest  city  of  the 
country,  and  one  of 
the  largest  and  busiest 
in  the  world.  Sinking 
of  the  land  (Fig.  459) 
has  caused  a  fine  har- 
bor with  extensive 
water  frontage.  This 
sinking  has  admitted 
the  sea  into  the  Hud- 
son (Fig. 462)  andinto 
several  small  tribu- 
taries, even  flooding 
low  divides,  thus 
forming  islands  which  add  greatly  to  the  water  front.  As  a 
result,  an  inclosed  waterway  has  been  formed  behind  Long 
Island,  opening  connection  with  New  England,  and  another 
along  the  Hudson  (Fig.  851)  into  the  interior.  The  latter 
route,  extended  to  the  Great  Lakes  by  canals  and  railways, 
has  concentrated  in  New  York  the  shipping  of  a  large  part 
of  the  interior  of  northern  United  States.  Thus  the  growth 
of  New  York  City  has  kept  pace  wj  i^h  the  growth  of  the  interior. 

The  peculiar  conditions  siirromidino^  this  rapidly  growing  city 
have  made  the  problem  of  living  there  difficult  to  solve.  The  har- 
bor is  in  two  states,  but  the  main  city  is  on  a  long,  narrow  island. 
There  is  no  space  for  the  population  to  easily  spread  outward 


Fig.  459. — New  York  City  andsurroundings,  show- 
ing the  submerged  channel,  which  extends  off- 
shore from  the  Hudson  to  the  edge  of  the  con- 
tinental shelf.  Before  the  land  was  lowered  the 
Hudson  occupied  this  channel. 


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PHYSIOGRAPHY  OF  UNITED   STATES. 


305 


in  various  directions  from  the  harbor,  as  in  many  cities.  Here, 
development  has  had  to  extend  up  the  narrow  island  and  across 
the  channels  of  the  harbor.  This  has  greatly  crowded  Manhattan 
Island,  and  has  forced  many  New  York  business  men  to  live  at  a 
distance,  large  numbers  going  across  North  River  to  New  Jersey 
or  across  East  River  to  Long  Island.  Therefore  a  number  of 
cities  have  grown  up  around  the  splendid  harbor,  such  as  Ho- 
boken  and  Jersey  City,  in  New  Jersey,  and  Brooklyn,  now  a  part 
of  New  York  City,  on  Long  Island.  The  problem  of  transporting 
these  people  is  more  ,|p^ 
serious  than  in  any 
other  city  ;  and  sur- 


face, elevated,  and 
underground  lines, 
added  to  bridges, 
ferry  boats,  and 
railway  trains,  are 
not  yet  sufficient.  As 
the  city  grows  'the 
problems  of  trans- 
portation increase. 


Fig.  462. — Ideal  restoration  of  the  neighborhood  of 
New  York,  if  the  land  were  reelevated  to  its 
former  level. 


Summary.  —  TJie 
Adlrondacks  re- 
semble   mountainous 

New  England  in  physiography  and  industries  ;  and  the  low,  hilly 
region  of  southeastern  New  York  resembles  southivestern  New  Eyig- 
land.  TJie  plateau  section  is  hilly,  sparsely  settled  on  the  uplands, 
but  with  better  soil,  and  more  inhabitants,  in  the  broad  valleys.  The 
lake-shore  plains  are  excellent  farming  land,  and  the  Erie  Canal  and 
the  railways  which  cross  these  plains  have  caused  the  growth  of  many 
towns  and  cities,  and  made  much  manufacturing  possible.  TJie  two 
cities  at  the  ends  of  this  route,  Buffalo  and  New  York,  have  become  of 
special  importance.  New  York  having  the  best  physiographic  situation 
of  all  the  cities  of  the  country,  and  hence  becoming  its  metropolis. 

196.    The  Coastal  Plains.  — ■  From  New  Jersey  to  Mexico 
there  is  a  narrow  belt  of  low,  level  land,  so  recently  raised 


306  NEW  PHYSICAL   GEOGRAPHY, 

above  the  sea  that  its  streams  are  young  and  large  tracts  are 
undrained  (Figs.  78,  79, 119-121).  This  coastal  plains  region 
is  broadest  in  Florida,  and  extends  up  the  Mississippi  val- 
ley, which  at  its  lower  end  is  a  filled  bay.  As  it  is  south  of 
the  glacial  belt,  rapids  and  falls  are  practically  absent  from 
the  streams  ;  but  there  are  lakes  in  the  irregularities  of  the 
raised  sea  bottom,  especially  in  Florida. 

Much  of  the  surface  is  too  sandy  for  farming  and  is  covered 
with  pine  forests  (p.  73).  Other  tracts  are  too  damp,  some  in  the 
South  being  the  seat  of  rice  culture,  which  requires  wet  ground. 
Where  the  soil  is  dry  and  fertile  enough,  the  coastal  plains  are 
the  seat  of  important  agriculture. 

There  is  httle  mineral  wealth  in  this  belt.  Sand  and  clay  are 
abundant,  and  in  some  cases  are  shipped  away  ;  and  at  Charleston 
and  in  Florida  there  are  important  beds  of  phosphate,  which  is 
sent  far  and  wide  for  use  as  land  fertilizer. 

The  coast  is  low  and  often  swampy,  especially  near  the  rivers, 
into  whose  mouths  the  sea  has  been  allowed  to  enter,  by  a  slight 
sinking  of  the  land  (Figs.  121,  124,  387).  There  are  some  good 
harbors  and  some  large  navigable  bays,  especially  in  the  north, 
where  the  sinking  has  been  greatest.  But  the  moving  sands,  and 
the  sand  bars  which  skirt  the  coast  (p.  214),  make  many  of  the  har- 
bors of  little  use.  The  larger  bays,  especially  Delaware  and  Chesa- 
peake bays,  admit  boats  far  into  the  land ;  and  because  of  their 
gentle  slope,  and  the  absence  of  falls  and  rapids,  mau}^  of  the  rivers 
are  navigable  to  small  boats.  Anywhere  on  the  level  surface,  roads 
and  railways  may  be  built;  but  the  sparseness  of  settlement,  and  the 
general  absence  of  manufacturing,  make  few  railways  necessary. 

The  cities  are  located  either  on  the  Fall  Line  (Fig.  125), 
along  the  inner  margin  of  the  coastal  plain,  or  at  the  head  or 
mouth  of  the  bays.  Thus,  Galveston  is  on  a  sand  bar  at  the 
mouth  of  a  bay  ;  New  Orleans  is  on  the  navigable  Mississippi 
at  the  point  where  it  comes  nearest  to  a  shallow  bay,  navi- 
gable in  early  times  by  small  boats  ;  Mobile,  Savannah,  and 
Charleston  are  on  small  bays  ;  Norfolk  is  at  the  mouth  of 
the  large  Chesapeake  Bay. 


PHJ blOGRAPHT  OF  UNITED   STATES.  807 

Summary.  —  TJie  level  coastal  plains  extend  from  New  Jersey  to 
Mexico.  They  are  often  so  swampy,  or  have  so  sandy  a  soil,  as  to 
be  unfit  for  agriculture.  There  is  little  mineral  wealth.  TJie  low, 
sandy  coast  has  many  navigable  bays,  due  to  sinking  of  the  land  ;  but 
sand  bars  iyiterferc  loith  the  entrance  to  many  by  ships.  The  chief 
cities  are  on  the  Fall  Line  or  on  the  coast,  either  at  the  head  or 
mouth  of  a  bay. 

197.  The  Piedmont  Belt.  —  The  low,  hilly  country,  from 
New  York  to  Alabama,  between  the  coastal  plains  and  the 
Ap]3alachians,  is  known  as  the  Piedmont  belt  (Figs.  461, 
464,  465).  It  is  an  uplifted  peneplain,  with  hilltops  rising 
to  a  nearly  uniform  level,  and  here  and  there  a  monadnock 
standing  above  the  general  surface.  An  uplift  has  given  the 
streams  power  to  sink  their  valleys  into  the  peneplain.  That 
this  was  once  a  high,  rugged,  mountain  region  is  proved  by 
the  fact  that  the  rocks  are  intensely  folded. 

Excepting  in  New  Jersey  the  Piedmont  region  is  south  of 
the  glacial  belt,  and,  therefore,  the  residual  soil  has  not  been 
removed  from  its  undulating  surface.  This  soil  is  usually 
deej)  and  fertile,  and,  since  the  climate  is  favorable  and  the 
surface  fairly  level,  this  is  a  splendid  agricultural  region.  It 
is  one  of  the  greatest  cotton  and  tobacco  belts,  and,  in  addi- 
tion, produces  fruits  and  farm  crops  of  various  kinds. 

The  Piedmont  belt  is  dotted  with  towns  and  cities,  and 
crossed  by  many  railway  lines.  The  Fall  Line  cities  (Fig. 
125)  are  'along  its  eastern  margin,  the  two  largest  being 
Philadelphia  and  Baltimore,  also  near  the  head  of  naviga- 
tion on  large  bays.  Washington  is  similarly  situated. 
Philadelphia  and  Baltimore,  like  Boston  and  New  York, 
have  become  great  seaports  because  of  good  harbors  and 
connection  with  a  productive  interior.  Being  shipping 
points  for  the  exports  and  imports  of  the  interior,  these 
cities  have  naturally  become  great  manufacturing  centers. 
Manufacturing  has  been  further  encouraged  by  the  readi- 
ness with  which  coal  and  iron  are  obtained. 


SOS 


NEW  PHYSICAL   OEOOHAPHy-. 


The  largest  city  away  from  the  Fall  Line  is  Atlanta,  which, 
like  many  other  towns  and  cities  of  the  South,  has  become  of 
importance  as  a  center  for  the  manufacture  of  cotton,  lumber, 
and  other  local  products.  Atlanta  owes  its  development  largely 
to  the  fact  that  it  lies  at  the  point  of  intersection  of  a  number 
of  railway  lines,  including  those  that  pass  around  the  southern 
end  of  the  Appalachians. 

Summary.  —  Tlie  Piedmont  belt  is  an  uplifted  peneplain,  ivith  a 
fertile  residual  soil  and  a  favorable  climate.  It  is,  therefore,  an 
excellent  agricultural  region,  producing  especially  tobacco  and  cotton. 
It  is  dotted  with  towns  and  cities,  the  largest  being  on  the  Fall  Line. 
Among  these  cities  are  Philadelphia,  Baltimore,  and  Washington, 
also  at  the  head  of  large  bays. 

198.  The  Appalachian  Belt.  —  This  belt,  extending  from 
New  York  to  Alabama,  parallel  to  the  Piedmont,  may  be 
divided  into  two  parts,  —  the  eastern,  or  Appalachian  proper, 
and  the  western,  or  Appalachian  (Alleghanj^)  plateau  (Figs. 

461,  461,  465). 
The  eastern  section 
is  a  true  mountain 
region  of  folded 
rock,  while  the 
western  portion  is 
true  plateau  with 
horizontal  strata. 
Ijoth  are  so  rugged 
that  much  of  their 
area  is  unsuited  to 
settlement  and, 
therefore,  still  for- 
est-covered (Figs.  85,  146).  The  ruggedness  is  due  to  so 
recent  an  uplift  that  the  streams  have  cut  deep  valleys. 

For  a  long  time  these  rugged,  forest-covered  belts  served 
as  a  barrier  to  westward  migration  ;  and  even  now,  along  all 
but  a  few  lines,  they  are  passed  with  difficulty.     The  ridges 


Fig.  463.  —  The  Potomac  Water  Gap. 


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PHYSIOGRAPHY  OF  UNITED   STATES,  309 

are  crossed  by  water  gaps  (Figs.  172,  192,  193,  463,  467), 
which  the  trails  of  the  Indians  and  trappers,  tlie  wagon 
roads  of  the  early  settlers,  and  the  railways  and  canals  of 
present-day  commerce  all  have  followed.  The  principal 
lines  of  passage  are  along  the  Cumberland,  Potomac,  Sus- 
quehanna, Delaware,  and  Mohawk  gaps. 

This  belt  includes  some  of  the  most  sparsely  settled  regions 
of  eastern  United  States  (p.  84),  and  is  an  important  timber 
reserve.  It  would  be  still  less  populous  if  it  were  not  for 
two  important  facts.  In  the  first  place,  wdiere  the  rock  is 
soft  the  valleys  have  been  so  broadened  as  to  invite  an 
agricultural  population  (Fig.  466).  This  is  best  illustrated 
by  the  broad,  fertile  limestone  valleys  of  New  Jersey,  Penn- 
sylvania, the  Shenandoah  valley  of  Virginia,  and  the  Ten- 
nessee valley.  In  the  second  place,  the  rocks  contain  stores 
of  valuable  mineral  (p.  108),  the  most  important  being  coal, 
iron,  oil,  and  gas.  The  coal  and  iron  have  been  exposed  in 
many  of  the  deep  valleys. 

These  conditions  have  led  to  the  development,  not  only  of 
mining  industries,  but  of  important  manufactured.  Of  the 
many  busy  centers  of  mining  and  manufacturing  the  great- 
est is  at  Pittsburg  and  Allegheny,  where  the  ]Monongahela 
and  Allegheny  unite  to  form  the  Ohio.  This  point  has 
water  connection  with  a  wide  area;  and  the  meeting  of  rail- 
ways where  the  valleys  come  together  has  added  facilities 
for  extensive  railway  transportation.  Therefore  iron  and 
other  raw  products  for  manufacture  are  easily  obtained,  and 
the  manufactures  are  readily  distributed.  This  favorable 
situation  was  caused  by  the  effect  of  the  ice  sheet  (p.  155). 

Scranton  and  Wilkes  Barre,  farther  east  in  the  anthracite  coal 
fields,  have  also  developed  into  important  mining  and  manufac- 
turing cities.  Indeed,  all  Pennsylvania  has  had  its  growth 
stimulated  by  its  great  mineral  resources,  and  especially  its  coal. 

Throughout  the  Appalachian  belt  similar  mineral  wealth  is  caus- 
ing development.     In  no  place  is  this  better  illustrated  than  at 


310  NEW  PHYSICAL   GEOGRAPHY, 

Birmingham,  Ala.,  where,  within  a  radius  of  a  few  miles,  are 
found  abundant  stores  of  coal,  iron,  and  limestone,  the  three 
materials  necessary  for  iron  smelting.  Under  such  favorable  con- 
ditions a  large  manufacturing  city  has  rapidly  grown. 

Summary.  —  Tlie  Appalacliian  belt,  extending  from  Neio  York  to 
Alabama,  consists  of{l)  true  mountains,  and  (2)  a  plateau  portiori. 
Both  are  for  the  most  jiart  rugged,  sparsely  settled,  and,  over  large 
areas,  forested,  forming  a  harrier  which  ivas  first  and  most  easily 
crossed  along  the  ivater  gaijs.  Some  of  the  broad  valleys  are  good 
farm  land,  and  there  is  much  mineral  ivealth,  especially  coal.  Tliis 
has  given  rise  to  a  number  of  important  miriing  and  manufactur- 
ing centers,  of  which  the  Pittsburg-Allegheny  region  is  most  im- 
portant. 

199.  The  Central  Plains. —  The  region  that  slopes  toward 
the  Mississippi  river,  from  the  Rocky  Mountains  on  one  side 
and  the  Alleghany  plateau  on  the  other,  is  for  the  most  part 
an  expanse  of  level  plains  (p.  76).  This  levelness  is  due  to 
two  facts:  (1)  the  rock  strata  are  nearly  horizontal;  (2)  the 
valleys  are  mature.  In  a  few  places  the  strata  have  been 
disturbed  by  mountain  folding,  as  in  the  Black  Hills  and 
the  low  mountains  of  central  Texas,  Indian  Territory, 
Arkansas,  and  southern  Missouri  (Fig.  461).  Around  Lake 
Superior  is  another  low  mountain  area,  a  southward  exten- 
sion of  the  ancient  mountain  land  of  central  Canada. 

In  so  level  a  country,  railwa3^s  may  be  built  almost  any- 
where, though  they  naturally  follow  the  valleys.  These  are 
so  broad  and  open  that  they  are  well  settled,  quite  unlike 
the  steep-sided  valleys  of  the  Alleghany  plateau.  The  large 
rivers  have  so  nearly  approached  grade  that  they  are  navi- 
gable for  long  distances.  The  Mississippi,  for  example,  is 
navigable  for  1000  miles  from  the  sea,  as  far  as  St.  Paul. 

The  ice  sheet  covered  the  northern  part  of  these  plains  (Fig. 
270),  filling  the  valleys  with  drift  and  thus  making  the  surface 
more  level  (Fig.  292).  These  glacial  deposits  have  turned  many 
«treams  out  of  their  valleys,  causing  falls  and  rapids,  as  in  th€ 


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PHTSIOGRAPHY  OF  UNITED   STATISTS, 


311 


case  of  the  Falls  of  St.  Anthony  at  Minneapolis.  Many  ponds 
and  lakes  were  also  formed,  as  in  the  low,  hilly  country  of  Minne- 
sota, in  which  there  are  said  to  be  10,000. 


27  -kiEs^iia     ni    m 


One  of  the  most  important  effects  of  the  glacier  was  to 
make  the  Great  Lakes  water  route  (p.  156)  which,  supple- 
mented by  canals,  offers  facilities  for  interior  water  trans- 
portation that  are  not  equaled  on  any  other  continent. 
Continuous  water 
transportation  is 
possible  from  the 
sea  to  Duluth,  a 
distance,  via  Mont- 
real, of  over  2000 
miles. 

The  generally 
level  surface,  the 
fertile  soil,  and 
the    climate    have 


legend; 

I  Considerable  Wheat  fialsed. 

I  Greatest  Wheat  Raising  District 


combined  to  make  Fig.  468.  — Notice  to  what  extent  the  wheat  of  the 
these     DlainS      one  country  is  raised  in  this  section.    Much  the  same 

(.     ,  f,  is  true  of  other  grains. 

of  the  greatest  of 

agricultural  regions  (Fig.  468).  The  further  fact  that  large 
sections  of  prairie  were  treeless  helped  in  the  rapid  devel- 
opment of  the  region.  The  agricultural  products  vary  with 
the  climate  from  hardy  grains  in  the  North  to  tobacco 
and  cotton  in  the  South.  In  the  hilly  lands  and  along 
the  rivers,  especially  in  Michigan,  Wisconsin,  and  Minne- 
sota, there  is  forest,  from  which  much  valuable  timber  is 
obtained. 

The  western  part  of  this  plains  region  (west  of  the  100th 
meridian)  has  an  arid  climate  (Figs.  127,  129),  unfitting  it 
for  agriculture  without  irrigation  (p.  287).  This  part  of 
the  Great  Plains  is  the  seat  of  an  important  grazing  industry 
(Fig.  128). 


312 


NEW  PHYSICAL   GEOGRAPHY. 


There  are  great  stores  of  mineral  wealth,  including  build- 
ing stone,  clay,  salt,  lead,  zinc,  oil,  gas,  and  coal ;  and  the 
copper  and  iron  of  the  Lake  Superior  region  contribute  to 
the  natural  resources.  The  almost  unlimited  supplies  of  coal, 
widely  distributed,  make  manufacturing  possible  throughout 
almost  the  entire 
area.  The  farms, 
mines,  and  forests 
supply  the  raw 
materials,  and  the 
excellent  facilities 
for  transportation 
permit  the  distri- 
bution of  raw  and 
manuf  ac  tured 
products. 

It  is  natural  that 
there  should  be 
busy  manufactur- 
ing cities  along  the  large,  navigable  rivers.  The  greatest  of 
these  river  cities  are  St.  Louis,  on  the  Mississippi,  near  the 
mouth  of  the  Missouri,  and  Cincinnati  and  Louisville,  on 
the  Ohio.  That  the  situation  of  St.  Louis,  near  the  junction 
of  two  great  rivers,  is  favorable,  is  shown  by  its  marvelous 
growth,  making  it  the  fourth  city  in  size  in  the  United 
States.  Its  position  makes  it  a  manufacturing  and  distrib- 
uting point  for  products  from  north,  south,  east,  and  west. 

Anotlier  great  industrial  community  is  found  at  the  head 
of  navigation  on  the  Mississippi  —  the  twin  cities  of  St.  Paul 
and  Minneapolis.  The  latter  has  the  further  advantage 
of  a  fall  in  the  Mississippi,  supplying  water  power.  New 
Orleans,  near  the  mouth  of  the  Mississippi  (p.  306),  and 
Pittsburg,  at  the  head  of  the  Ohio  (p.  309),  are  closely 
related  in  prosperity  to  the  fertile  interior  plains,  for  they 
^re  in  close  communication  with  them  by  water  and  rail. 


Fig.  469.  —  Sketch  map  to  show  the  variety  of  mate- 
rials available  for  shipment  by  the  Great  Lakes. 


PHYSIOGRAPHY  OF  UNITED  STATES.  313 

Along  the  lake  route  many  important  cities  have  de- 
veloped :  in  Canada,  Montreal  and  Toronto  ;  in  United 
States,  Buffalo,  Cleveland,  Toledo,  Detroit,  Chicago,  Mil- 
waukee, and  the  two  neighboring  cities  of  Duluth  and 
Superior,  besides  many  smaller  places.  Each -of  these  cities 
profits  by  the  commerce  that  the  water  route  opens  to  it;  and 
each  is  able  to  receive  the  raw  products  of  the  entire  lake 
region  (Fig.  469).  Iron,  one  of  the  most  important  of  these 
products,  must  be  brought  to  the  coal  fields  for  smelting, 
and  all  lake  ports  near  the  coal  fields  share  in  the  benefit. 
With  the  recent  wonderful  development  of  the  iron  region 
there  has  been  a  corresponding  growth  of  the  lake  ports. 

Each  of  these  cities  has  some  special  reason  for  its  growth 
at  that  particular  point.  Duluth-Superior  and  Buffalo  are 
at  the  two  American  ends  of  the  lake  route.  Toronto  is  on 
a  good  harbor  on  the  Canadian  side  of  Lake  Ontario,  oppo- 
site the  Welland  Canal.  Montreal  is  at  the  head  of  navi- 
gation for  large  ocean  vessels,  and  at  the  foot  of  rapids  in  the 
St.  Lawrence,  around  which  a  canal  has  been  built.  Cleve- 
land and  Toledo  are  on  good  harbors  on  Lake  Erie,  and  near 
extensive  coal  fields.  Detroit  is  on  a  narrow  strait,  through 
which  lake  traffic  must  pass,  and  at  a  point  where  railways 
cross  from  United  States  to  Canada.  It  is,  moreover,  prac- 
tically at  one  end  of  Lake  Erie.  Milwaukee  is  on  a  good 
lake  harbor  backed  by  a  fertile  country. 

Of  all  the  cities  in  this  section,  Chicago  has  the  best 
natural  site  and  has,  therefore,  grown  the  fastest.  It  is  no 
accident  that  it  has  become  the  second  city  of  the  country  in 
size ;  nor  is  there  reason  to  expect  that  its  growth  will  not 
continue.  The  small  harbor,  around  which  Chicago  started, 
was  scoured  out  by  the  overflow  stream  of  the  glacial  lakes 
tliat  existed  while  the  ice  sheet  was  melting  away  (Fig.  280). 
The  city  soon  outgrew  its  small  natural  harbor,  but  continued 
to  prosper  because  of  its  favorable  situation. 

Like  Buffalo,  Toledo,  Detroit,  and  Duluth,  it  occupies  a 


314  NEW  PHYSICAL   GEOGRAPHY. 

position  near  the  end  of  a  great  lake.  With  other  lake  ports 
it  shares  all  the  advantages  of  lake  shipping;  and,  like  sev- 
eral of  them,  it  is  near  coal  fields,  and  in  the  midst  of  a 
fertile  agricultural  region  which  supplies  raw  products  and 
a  market  for  manufactured  goods.  More  than  this,  it  is  a 
natural  railway  center;  railroads  from  the  East  swing  around 
the  southern  end  of  Lake  Michigan  to  reach  Chicago,  where 
they  unite  with  railroads  from  other  sections.  For  these 
reasons  Chicago  has  become  a  great  manufacturing  and  com- 
mercial center,  being  a  distributing  point  for  a  wide  area  of 
country.  It  is  a  center  of  distribution  for  some  products,  such 
as  meat  products,  for  cities  even  as  far  away  as  the  seacoast. 

Summary.  —  The  Great  Plains  region,  thougJi  mostly  level,  has  a 
few  low  mountainous  sections.  The  northern  portion  was  covered 
hy  the  ice  sheet.  Tlie  greater  part  of  the  plains  region  is  adaj^ted  to 
agriculture;  but  some  of  the  more  hilly  portions  are  forested.  Tlie 
western  portion  is  arid,  and  hence  devoted  mainly  to  grazing. 
Tlie  Plains  have  great  mineral  resources,  notably  coed  and  iron,  and 
consequently  have  become  an  important  manufacturing  section.  Tlie 
navigable  rivers  and  broad  valleys  have  encouraged  the  growth 
of  a  number  of  large  river  cities  of  tchich  St.  Louis  is  the  greatest. 
Tlie  Great  Lakes  water  route  is  even  more  important  for  navigation, 
and  hence  has  a  series  of  large  and  busy  manufacturing  cities.  Of 
these  Chicago  is  the  largest.  This,  the  second  city  in  the  country,  has 
a  Jine  natural  situation  at  the  end  of  one  of  the  lakes,  in  the  midst  of  a 
fertile  agricultural  country,  and  near  extensive  coed  fields. 

200.  The  Far  West.  —  This  broad  area  is  mainly  a  great 
plateau  with  mountain  ranges  rising  here  and  there.  Both 
the  mountains  (Figs.  158,  161,  165,  166,  470,  471)  and  pla- 
teaus (Figs.  137,  138,  141,  476-478)  are  so  young  that  they 
ai-e  very  rugged.  Yet  there  are  many  broad  mountain  val- 
leys and  extensive  areas  of  level  plateau,  so  that,  if  the  cli- 
.mate  favored,  this  might  become  much  more  important  as 
an  agricultural  region.  Over  most  of  this  area  the  climate 
is  so  arid  tliat  the  land  is  suited  only  to  grazing;  and  vast 


FiQ.  470.  — A  view  in  the  Rocky  Mountains  ui  Oulorado,  ueai-  the  timber  line, 
showing  the  steep  slopes  and  small  amount  of  surface  available  for  farming. 


Fra.  471.  —  A  railway  line  crossing  the  Rocky  Mountains  near  Georgetown.  Colo. 


fin.  472.-4.  trail  in  the  mountains  of  western  United  States. 


PHYSIOGRAPHT  OF  UNITED  STATES.  315 

numbers  of  cattle,  sheep,  horses,  and  goats  are  raised  on  the 
plains,  plateaus,  and  mountain  slopes.  Parts  of  Nevada, 
southern  California,  and  Arizona  are  true  deserts,  with  too 
little  grass  and  water  even  for  grazing  (Fig.  150). 

On  the  other  hand,  some  of  the  high  plateaus  and  moun- 
\^ain  valleys  have  rainfall  enough  for  agriculture,  and  many 
of  the  mountain  slopes  and  higher  plateaus  are  forested. 
One  very  large  area,  including  the  northern  half  of  Cali- 
fornia, western  Oregon,  and  much  of  Washington,  has  suffi- 
cient rainfall  to  make  it  a  very  important  agricultural  region. 

Farming  is  also  carried  on  wherever  irrigation  is  possible; 
but,  unfortunately,  the  water  supply  is  lowest  in  summer.  One 
of  the  great  problems  of  the  future,  in  which  the  entire  country  is 
interested,  is  how  to  store  the  winter  rain  and  melting  snow  for 
use  in  summer.  The  government  is  now  at  work  on  this  problem, 
and  reservoirs  are  being  built  which  will  supply  water  to  reclaim 
thousands  of  square  miles  of  arid  land.  In  this  way  the  West  may 
be  made  to  support  a  much  larger  population. 

The  mountain  rocks  contain  great  stores  of  mineral,  only- 
portions  of  which  have  been  developed.  No  part  of  the  world 
equals  this  section  in  the  production  of  precious  metals  ;  and, 
in  addition,  much  copper,  lead,  and  zinc  are  obtained.  Coal, 
oil,  gas,  iron,  salt,  building  stone,  and  many  other  mineral 
products,  though  found  in  many  places,  are  not  yet  produced 
in  large  quantities.  They  are  among  the  undeveloped  re- 
sources of  United  States. 

Scattered  through  the  Far  West  are  many  thriving  towns 
and  cities  (Figs.  133,  190),  some  engaged  in  mining,  some 
in  manufacturing,  and  all  serving  as  distributing  centers  for 
surrounding  sections.  Of  these  the  largest  are  Denver,  at 
the  eastern  base  of  the  Rocky  Mountains,  Salt  Lake  City  in 
Utah,  and  several  cities  on  the  Pacific  slope.  Denver  is  a 
railway  center  and  an  important  distributing  and  manufac- 
^ring  center  for  a  great  mineral  section. 


816  NEW  PHYSICAL   GEOGRAPHY, 

On  the  Pacific  slope  are  Seattle,  Tacoma,  and  Portland, 
manufacturing  and  shipping  points  for  a  productive  agri- 
cultural country.  Their  harbors,  like  that  of  San  Francisco 
(Fig.  350),  have  been  caused  by  sinking  of  the  land.  The 
great  agricultural  and  mineral  resources  of  California  have 
made  San  Francisco  a  busy  manufacturing  and  shipping 
center,  already  ranking  in  size  as  the  ninth  city  in  the 
country.  With  the  growing  trade  across  the  Pacidc,  this 
city  seems  destined  to  take  a  still  higher  rank. 

The  Far  West  is  justly  noted  for  its  magnificent  scenery.  No 
part  of  the  world  rivals  in  grandeur  the  canyon  of  the  Colorado 
(Figs.  1,  139,  478) ;  in  no  part  of  the  world  is  there  the  equal  of 
the  Yellowstone  Park,  with  its  hot  springs  (Figs.  243,  474),  gey- 
sers (Figs.  244,  473),  and  canyons  (Fig.  480) ;  nowhere  is  there 
another  Yosemite  (Fig.  475).  But  these  are  only  some  of  the 
best  known  of  the  points  of  scenic  interest  in  the  West.  Sym- 
metrical volcanic  cones  (Figs.  214,  215),  rugged  peaks  and  glaciers, 
and  grand  mountain  valleys  (Figs.  57,  66,  472)  and  lakes,  whose 
surroundings  are  nowhere  excelled  in  picturesqueness,  are  found 
in  various  parts  of  the  West.  Each  year  the  stream  of  travel 
toward  these  centers  of  scenic  attraction  increases. 

The  dry  climate,  unfavorable  to  agriculture,  is  favorable  to 
health;  and,  consequently,  many  parts  of  the  West  —  Colorado, 
New  Mexico,  Arizona,  and  southern  California,  especially  —  are 
much  frequented.  The  city  of  Los  Angeles  owes  a  large  part 
of  its  growth  to  the  number  of  people  who  have  gone  there  in 
-  search  of  a  healthful  climate.  The  climate  of  southern  California 
is  so  sunny  and  balmy,  like  that  of  the  Mediterranean,  that, 
wherever  irrigation  is  possible,  the  orange  grows  to  perfection. 
It  is  one  of  the  most  attractive  parts  of  the  country. 

Summary.  —  Except  in  the  northivestern  part,  aiid  on  some  high 
jjlateaus  and  mouyitain  slopes,  the  plateau  and  mountain  area  of 
the  West  has  a  climate  too  dry  for  agriculture  without  irrigation. 
Much  of  it  is,  therefore,  essentially  a  grazing  region.  TJie  building 
of  reservoirs,  to  store  the  winter  and  spring  floods  for  use  in  summer, 
is  greatly  increasing  the  area  of  agricultural  land.     The  West  is  an 


|f|«l>.i.ULIIt«*  I JrljU|l^i||i. 


Fig.  473.  —  Eruption  of  Fountain  geyser  in  the  Yellowstone  Park. 


Fig.  474.  —  The  Hot  Springs  near  the  entrance  to  Yellowstone  Papk. 


")    ^^Q.  475.  —  Granite  peaks  in  the  Yosemite  valley,  California. 


PHYSIOGRAPRT  OF  UNITED  STATES.  317 

important  mineral  belt,  being  the  greatest  producer  of  precious  metals 
in  the  world.  Of  the  cities,  the  largest  in  the  eastern  Rockies  is 
Denver.  On  the  Pacific  slope  are  several  cities,  of  ivhich  Sail  Fran- 
cisco is  the  largest,  hewing  a  fine  location,  on  a  splendid  harbor,  the 
outlet  of  a  productive  country.  The  West  is  iioted  for  its  ivonderful 
scenery,  especially  the  Colorado  Canyon^  Yelloic stone  Park,  and 
Yosemite  valley  ;  the  arid  climate  also  makes  the  Southwest  a  favorite 
health  resort. 

Topical  Outline  and  Review  Questions. 

Topical  Outline.  — 194.  New  England.  —  (a)  Surface  features: 
rocks:  effect  of  denudation  ;  monadnocks;  uplift;  nature  of  valleys;  min- 
eral products,  (b)  Farming :  glacial  soil ;  reasons  for  forests  ;  small  farms ; 
food  supply,  (c)  Manufacturing:  water  power;  lakes,  (d)  Coastline: 
cause  for  irregulai'ity ;  fishing;  ship  building;  summer  resorts;  naviga- 
tion ;  effect  oo  manuf actliring ;  comparison  with  Norway,  (e)  Cities : 
location;  Boston;  reasons  for  growth.  (f}  Comparison:  with  Scan- 
dinavia; with  Great  Britain. 

195.  New  York. —  (a)  General  features:  four  divisions;  glacial 
action ;  agriculture ;  mineral  resources ;  manufacturing,  (b)  Adiron- 
dacks :  forests;  manufacturing;  mineral;  summer  resorts,  (c)  Plateau 
region:  uplands;  valleys;  agriculture;  railways;  cities.  (d)  Lake 
plains  :  cause  of  levelness ;  farming ;  Erie  Canal  route ;  cities ;  valleys 
leading  into  the  plateau,  (e)  Largest  two  cities  :  influence  of  canal ; 
causes  of  growth.  (/)  New  York  :  cause  of  harbor;  water  communi- 
cation with  New  England ;  with  the  interior  ;  peculiar  situation ;  effect 
on  homes ;  on  transportation. 

196.  The  Coastal  Plains.  —  Extent;  surface  features  ;  agriculture;  min- 
eral wealth ;  coast  line  ;  interior  navigation ;  railway  transportation ;  loca- 
tion of  cities ;  instances. 

197.  The  Piedmont  Belt.  —  Surface  features;  peneplain;  soil;  agri- 
culture; Fall  Line  cities;  Philadelphia  and  Baltimore ;  Atlanta. 

198.  The  Appalachian  Belt. —  (a)  Surface  features  :  extent;  two  divi- 
sions; ruggedness;  effect  as  barriers  ;  river  gaps,  (b)  Industries:  lum- 
ber ;  agriculture  ;  mineral  resources,  (c)  Cities  :  Pittsburg  and  Allegheny ; 
Scranton  and  Wilkes  Barre ;  Birmingham. 

199.  The  Central  Plains.  —  (a)  Surface  features :  extent ;  cause  of  lev- 
elness ;  mountain  areas ;  broad  valleys ;  navigable  rivers ;  effect  of  glacier ; 
Great  Lakes  water  route.  (b)  Industries:  agriculture;  lumbering; 
grazing;  mineral  resources;  manufacturing,  (c)  River  cities  :  St.  Louis  ; 
Cincinnati ;  Louisville  ;  advantages  of  location  of  St.  Louis ;  St.  Paul  and 


318  NEW  PHYSICAL   GEOGRAPHY, 

Minneapolis;  New  Orleans;  Pittsburg,  (d)  Lake  cities:  cities  on  the 
lakes;  importance  of  situation  on  the  lakes;  location  of  Duluth-Supe- 
rior;  Buffalo;  Toronto;  Montreal;  Cleveland;  Toledo;  Detroit;  Mil- 
waukee; Chicago,  —  origin  of  harbor,  position,  commerce,  surrounding 
country,  railway  center,  manufacturing  and  distributing  center. 

200.  The  Far  West.  —  (a)  Surface  features:  plateaus;  mountain 
ranges.  (b)  Climate  and  agriculture:  arid  climate,  —  grazing,  desert; 
humid  sections, — location,  forests,  agriculture;  irrigation;  storage  reser- 
voirs, (c)  Mineral:  precious  metal;  other  minerals,  (d)  Cities:  Den- 
ver; Seattle;  Tacoma;  Portland;  San  Francisco,  —  its  harbor,  region 
tributary,  growth  of  city,  (e)  Scenery:  Colorado;  Yellowstone;  Yosem- 
ite;  other  attractions.     (/)  Health:  favorable  climate ;  Los  Angeles. 

Review  Questions.  — 194.  What  are  the  surface  features  of  the  up- 
lands V  What  is  a  monadnock  ?  What  is  the  condition  of  the  valleys  ? 
Why  ?  What  mineral  products  are  there  ?  What  effects  had  the  ice  sheet 
on  the  soil  ?  Explain  the  condition  of  farming.  What  effect  has  this  on 
food  supply?  What  conditions  have'favored  manufacturing?  Explain 
the  irregular  coast.  Wliat  important  effects  has  this  coast?  Where  are 
the  cities  located?  What  conditions  have  favored  the  growth  of  Boston? 
Compare  New  England  with  Scandinavia  and  Great  Britain. 

195.  What  are  the  four  divisions  of  the  state?  What  effect  has  the 
glacier  had?  What  are  the  natural  resources?  What  is  the  condition 
and  what  are  the  industries  of  the  Adirondacks?  What  is  the  condition 
on  the  plateau  upland?  In  the  valleys?  Where  are  the  cities  of  the 
plateau  section?  What  causes  the  levelness  of  the  lake  plains?  What 
are  the  industries  there?  What  effect  has  the  Erie  Canal?  What  is  the 
condition  of  the  valleys  leading  into  the  plateau?  Why  have  cities 
grown  at  the  two  ends  of  the  water  route  ?  What  conditions  of  physiog- 
raphy have  favored  the  growth  of  New  York  City  ?  What  effect  has  the 
peculiar  location  of  the  city  on  homes?     On  transportation? 

196.  What  is  the  condition  of  the  coastal  plains?  What  about  agri- 
culture? Mineral  wealth?  What  is  the  condition  of  the  coast  line? 
What  favors  internal  navigation?     Where  are  the  cities? 

197.  Explain  the  surface  features  of  the  Piedmont  belt.  What  is  the 
condition  of  agriculture?  What  accounts  for  the  greatness  of  Phila- 
delphia and  Baltimore?     What  accounts  for  the  growth  of  Atlanta? 

198.  What  are  the  two  divisions?  What  are  the  surface  features? 
How  is  this  rugged  barrier  crossed  ?  What  are  the  resources  of  the  belt? 
What  conditions  have  favored  the  growth  of  Pittsburg  and  Allegheny? 
Scranton  and  Wilkes  Barre?     Birmingham  ? 

199.  Why  are  these  plains  level?  Where  are  the  mountainous  sec- 
tions ?    Why  are  the  rivers  favorable  to  navigation,  and  the  valleys  to 


PHYSIOGRAPRr  OF  UNITED   STATES.  319 

settlement?  What  effects  had  the  ice  sheet?  Of  what  importance  is 
the  lake  route?  What  conditions  favor  agriculture?  Where  are  forests 
found?  What  is  the  condition  in  the  western  part?  What  important 
mineral  resources  are  there?  What  conditions  favor  manufacturing? 
Locate  the  three  largest  river  cities.  How  is  the  situation  of  St.  Louis 
especially  favorable?  What  advantages  of  location  have  St.  Paul  and 
Minneapolis?  How  are  New  Orleans  and  Pittsburg  related  to  this 
region  ?  Name  and  locate  the  leading  lake  cities.  What  general  advan- 
tages do  they  share?  What  especial  reason  is  there  for  the  growth  of 
each?  What  is  the  reason  for  the  exact  location  of  Chicago?  What 
special  advantages  has  it? 

200.  What  are  the  surface  features  ?  What  is  the  general  condition 
of  the  climate  ?  What  is  the  effect  of  this  on  industry?  Where  are  the 
humid  sections  ?  Why  are  storage  reservoirs  necessary?  What  valuable 
minerals  are  found  ?  For  what  is  Denver  important  ?  Seattle,  Tacoma, 
and  Portland  ?  What  causes  the  harbors  ?  What  has  favored  the  growth 
of  San  Francisco?  What  scenic  attractions  are  there  in  the  West?  In 
what  way  is  the  dry  climate  favorable?  What  effect  has  this  had  on 
Los  Angeles  ? 

Reference  Books.  — Powell,  Physiographic  Regions  of  the  United  States, 
National  Geographic  Monographs,  American  Book  Co.,  New  York,  1895, 
$2.50;  Shaler,  United  States  of  America,  Appleton  &  Co.,  New  York, 
1894,  $10.00  ;  Mill,  International  Geography,  Appleton  &  Co.,  New  York, 
1899,  $3.50 ;  Tarr  Sf  McMurry  Geographies,  Second  Book,  Macmillan 
Co.,  New  York,  1900,  $0.75 ;  Davis,  Physical  Geography  of  Southern 
New  England,  National  Geographic  Monographs,  American  Book  Co., 
New  York,  1895,  $2.50;  Emerson,  New  England  Supplement,  Tarr  Sf 
McMurry  Geographies,  Macmillan  Co.,  New  York,  1901,  $0.30;  Tarr, 
Physical  Geography  of  New  York  ^Sto/e,  Chapter  I,  Physiographic  Features, 
Macmillan  Co.,  New  York,  1902,  $3.50;  Same,  Chapter  XII,  Influence  of 
Physiographic  Features  upon  Industrial  Development;  Whitbeck,  New 
York  Supplement,  Tarr  ^  McMurry  Geographies,  Macmillan  Co.,  New 
York,  1901,  $0.30  (also  other  State  Supplements  to  Tarr  &  McMurry 
Geographies)  ;  Kemp,  Ore  Deposits  of  United  States  and  Canada,  En- 
gineering and  Mining  Journal,  New  York,  1893,  $4.00;  Tarr,  Economic 
Geology  of  United  States,  Macmillan  Co.,  New  York,  fourth  edition,  1903, 
$3.50. 


CHAPTER   XVI. 

RIVERS    OF   UNITED    STATES. 

Almost  the  entire  United  States  is  tributary  to  seven 
large  river  systems  (Fig.  479)  and  a  series  of  smaller  streams, 
most  of  which  flow  eastward  or  southward  into  the  Atlantic 
and  Gulf.  The  greatest  amount  of  drainage  is  into  the 
Atlantic,  including  the  Mississippi,  which  drains  two  fifths 
of  the  whole  country  ;  next  in  area  is  the  Pacific  drainage ; 
while  a  small  section  drains  into  the  Arctic  through  the  Red 
River  of  the  North.  As  has  been  shown  in  previous  chap- 
ters, the  river  systems  have  been  highly  important  factors  in 
the  development  of  the  country.  They  have  been  a  source 
of  food ;  they  have  supplied  water  power ;  and  they  have 
served  as  pathways  of  exploration  and  commerce.  The 
present  chapter  considers  this  subject  more  specifically. 

201.  The  Columbia.  — The  Columbia  rises  on  the  western 
slopes  of  the  Rocky  Mountains,  flows  across  an  arid  region, 
and  enters  the  sea  in  a  region  of  abundant  rainfall.  Its 
length  is  1400  miles,  and  it  drains  over  200,000  square 
miles.  The  lower  Columbia  is  formed  bv  the  union  of 
two  rivers,  the  Columbia  and  Snake.  From  the  Rocky 
Mountains  to  the  Cascades,  both  the  Snake  from  the  south 
and  the  Columbia  from  the  north  flow  across  a  vast  lava 
plateau  (p.  125).  These  rivers  and  their  tributaries  have 
cut  young  canyon  valleys  in  this  plateau  (Fig.  476),  in  some 
places  2000  to  3000  feet  deep,  out  of  which  it  is  impossible  to 
lead  the  water  for  irrigation.  There  are  many  rapids  and 
falls,  including  the  Shoshone  Falls,  so  that,  throughout  the 
greater  part  of  their  course,  the  rivers  are  unnavigable. 


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BIVEBS   OF  UNITED  STATES,  321 

Instead  of  serving  as  pathways,  these  canyon  valleys  are 
barriers  to  passage  ;  but  in  its  lower  course  the  Columbia 
is  an  important  aid  to  travel,  for  it  crosses  both  the  Cascade 
and  Coast  Ranges,  thus  opening  gaps  across  these  moun- 
tains, which  a  railway  follows.  Sinking  of  the  land  has 
admitted  the  tide  for  over  100  miles,  as  far  as  Portland; 
and  navigation  by  river  boats  is  possible  up  the  river  even 
above  the  junction  of  the  Columbia  and  Snake  (Fig.  481). 

Large  numbers  of  salmon  pass  up  this  river  to  lay  their  eggs, 
or  spawn ;  and  the  catching  and  canning  of  these  fish  is  an  im- 
portant industry  along  the  lower  course  of  the  Columbia. 

Summary. — The  union  of  the  Columbia  and  Snake  rivers  makes 
a  great  river  system.  In  their  upper  parts  these  rivers  occupy  canyons 
in  a  broad  lava  plateau,  and  these  valleys  are  barriers  to  travel;  but 
the  lower  river  is  navigable,  opening  a  pathway  across  the  moun- 
tains, and  admitting  ocean  boats  for  100  miles,  as  far  as  Portland. 

202.  The  Sacramento.  —  The  extensive  fertile  valley  of 
California  (Fig.  114),  between  the  Sierra  Nevada  and  Coast 
Ranges,  is  drained  by  the  Sacramento  River  where  it  crosses 
the  mountains  at  the  Golden  Gate.  Sinking  of  the  land  has 
admitted  the  sea,  forming  San  Francisco  Bay  and  connecting 
the  valley  of  California  with  the  sea  (Fig.  350).  The  Sacra- 
mento is  400  miles  long  and  has  a  drainage  area  of  about 
58,000  square  miles.  It  is  made  by  the  union  of  two  rivers 
which  extend  along  the  great  valley,  —  the  Sacramento  from 
the  humid  north,  the  San  Joaquin  from  the  arid  south.  For 
some  distance  each  is  navigable  to  small  boats. 

These  rivers  are  fed  by  short  streams  from  the  inclosing  moun- 
tains, where  they  occupy  canyons.  At  the  base  of  the  mountains 
these  tributaries  are  building  low  alluvial  fans,  and  are  engaged  in 
slowly  filling  the  great  valley  (p.  68).  Over  the  alluvial  fans  the 
streams  flow  in  shallow  valleys,  from  which  water  is  easily  led  for 
purposes  of  irrigation.  The  water  of  the  mountain  streams  is  also 
used  in  hydraulic  mining  for  washing  gold  from  the  river  gravels. 


322  NEW  PHYSICAL   GEOGRAPHY, 

Summary.  —  TJie  Sacramento,  fonned  by  union  of  the  Sari  Joaquin 
und  Sacramento,  is  fed  by  small  mountain  streams  whose  water  is 
useful  for  irrigation  and.  for  hydraulic  mining.  Breakiyig  through 
the  Coast  Ranges  at  the  Golden  Gate,  this  river  connects  the  great 
California  valley  icith  the  ocean. 

203.  The  Colorado. —  The  Colorado  River,  like  the  Nile, 
has  its  source  among  mountains  which  supply  it  with  so 
much  water  that  it  is  able  to  flow  completely  across  a  vast 
stretch  of  arid  and  desert  country.  Its  length  is  about  2000 
miles,  and  it  drains  about  225,000  square  miles,  being  formed 
by  the  union  of  two  large  streams,  —  the  Grand  and  Green. 
For  fully  half  its  length  the  Colorado  flows  in  canyons  cut  in 
a  high  plateau,  which  in  places  is  over  8000  feet  above  sea 
level.  The  depth  of  the  canyons  varies  from  a  few  hundred 
feet  to  over  6000  feet  in  the  Grand  Canyon,  which  is  over 
200  miles  long  (p.  82).  At  the  lower  end  of  the  Grand 
Canyon  the  country  becomes  open  and  the  river  crosses  fully 
300  miles  of  desert  to  the  Gulf  of  California.  In  its  lower 
course  the  river  flows  over  a  floodplain  and  delta. 

Without  exception  the  Colorado  is  the  most  remarkable  river 
in  the  world  (Figs.  1,  139,  477,  478).  No  other  canyon  equals 
the  Grand  Canyon  in  size  or  grandeur.  For  long  distances  it  is 
impossible  to  descend  to  its  bottom  over  the  precipitous  sides, 
and  the  canyon  forms  an  absolute  barrier  to  travel.  It  would 
make  an  excellent  boundary  between  countries.  Only  by  under- 
going the  utmost  hardships  and  dangers  is  it  possible  to  pass 
through  the  canyon,  and  few  explorations  in  America  have  been 
more  daring  than  that  of  Major  Powell's  party,  which  made  the 
first  descent  (Fig.  139). 

On  both  sides  rise  steep,  impassable  precipices,  often  from  the 
water's  edge  ;  and  the  river  tumbles  over  a  succession  of  rapids,  in 
which  it  is  ahnost  impossible  for  a  boat  to  live.  Here  and  there 
short  tributaries  enter,  with  slopes  so  steep  that  tlie  oncasinnA! 
heavy  rains  wash  large  t)owiders  down  tbem  into  the  mam  streaau. 
These  form  one  of  the  chief  causes  for  the  rapids. 

A  mile  of  successive  rock  strata  is  revealed  in  this  enormou? 


RIVERS  OF  UNITED  STATES. 


325 


gash  in  the  crnst,  and  at  their  base  is  a  buried  mountain  area, 
once  dry  land,  now  covered  by  a  thick  series  of  sedimentary 
strata.  The  river  is  flowing  with  so  steep  a  slope  that  it  is 
rapidly  cutting  its  canyon  deeper,  and  weathering  is  wasting 
back  the  cliffs,  which  form  a  multitude  of  irregular  and  rugged 
mesas,  buttes,  ridges,  and  spurs.  Where  hard  rocks  outcrop,  there 
are  steep  cliffs ;  where 
weaker  layers  occur,  the 
slopes  are  gentler ;  where 
the  cliffs  have  wasted 
back,  flat  terraces  often 
extend  from  their  base ; 
and  everywhere  there  is  a 
wonderful  and  varied  col- 
oring of  the  rock  walls. 
In  places,  where  the  cliffs 
have  wasted  back,  the  can- 
yon slope  consists  of  a 
series  of  hard  rock  terraces 
with  level  tops  and  steep 
fronts.  This  is  especially 
true  of  the  older,  upper 
portion  where  the  cliffs 
have  wasted  farther  back. 
In  this  arid  country  few 
large  tributaries  enter  the 
river,  and  these  bring  little 
water,  for  throughout  most 

of  the  area  the  annual  rainfall  is  less  than  10  inches.  All  the 
larger  tributaries  are  from  the  southern  and  eastern  sides,  because 
the  river  flows  so  near  the  edge  of  the  arid  Great  Basin  that  tribu. 
taries  from  that  side  must  be  few  and  small.  These  tributaries 
themselves  are  in  canyons,  and  between  them  are  broad  areas  of 
tableland  with  many  mesas  and  buttes,  —  a  typical  young,  arid 
land  plateau  (p.  81). 

Summary.   —  The   Colorado,  fed  by  rains  and  snoics  from  the 
Rocky  Mountains,  Jlows  for  nearly  2000  miles  across  an  arid  and, 


Fig.   478.  —  A  view  in   tlie  Marble  Canyon, 
one  of  the  canyons  of  the  Colorado. 


324  NEW  PHYSICAL   GEOGRAPHY. 

in  places,  a  desert  country,  for  a  large  part  of  the  distance  in  deep 
canyons  sunk  in  the  2^latea2(.  The  Grand  Canyon  has  a  depth  of 
6000  feet.  Its  steep  sides  are  often  impassable,  and  they  are  carved 
and  scidptured  into  a  great  variety  of  forms.  There  are  feiv  large 
tributaries,  and  these  bring  little  icater. 

204.  The  Great  Basin.  —  The  Great  Basin,  a  region  of  interior 
drainage  with  an  area  of  over  200,000  square  miles,  lies  between 
the  Kooky  and  Sierra  Nevada  mountains.  It  is  bounded  on  the 
north  by  the  Columbia  plateau,  and  on  the  south  by  the  Colorado 
plateau.  A  number  of  disconnected  parts  unite  to  form  this 
general  basin,  one  of  them.  Death  Valley,  being  below  sea  level. 
The  surface  of  the  Great  Basin  is  crossed  by  a  number  of  short 
mountain  ranges,  known  as  the  Basin  Ranges. 

The  entire  region  is  arid,  and  in  places  a  true  desert  (Fig.  150). 
The  short,  mountain  streams  quickly  disappear,  either  by  evapo- 
ration or  by  percolation  into  the  loose  gravels  of  their  alluvial 
fans.  Some  of  the  streams  terminate  in  salt  lakes,  such  as  Great 
Salt  Lake ;  others  in  alkali  flats  or  playa  lakes  (p.  169). 

There  is  too  little  water  for  extensive  irrigation,  and,  conse- 
quently, most  of  the  Great  Basin  is  sparsely  settled.  The  most 
thickly  settled  part  is  the  fertile,  irrigated  region  of  which  Salt 
Lake  City  (Fig.  133)  is  the  center.  If  the  rainfall  were  greater, 
water  would  gather  in  the  basins,  forming  several  hundred  lakes. 
During  the  glacial  period,  when  the  climate  of  the  Great  Basin  was 
moist,  large  fresh-water  lakes  filled  some  of  these  basins  (p.  164). 

Summary. —  Tlie  Great  Basin  is  an  arid  region  of  interior  drain- 
age, consisting  of  a  number  of  smaller  basins.  It  is  in  places  true 
desert,  and,  for  the  most  j^cirt,  sparsely  settled. 

205.  The  Rio  Grande. — This  river  resembles  the  Colorado  in 
some  respects.  It  is  almost  as  long  (1800  miles),  and  has  a  greater 
drainage  area  (240,000  square  nnles).  Like  the  Colorado,  the 
Rio  Grande  receives  so  large  and  permanent  a  water  supply  from 
its  mountain  sources  that  it  is  able  to  flow  across  an  arid  country 
to  the  sea.  Like  the  Colorado,  too,  it  has  cut  deep  canyons  in  the 
plateau ;  but  they  are  neither  so  deep,  so  long,  nor  so  continuous 
as  the  canyons  of  the  Colorado.     In  a  number  of  sections  the 


'.:*^ 


RlvEBS   OF  UNITED   STATES.  325 

valley  broadens,  and  is  bordered  by  floodplains  and  low,  terraced 
land,  over  which  the  river  water  is  easily  led  for  irrigation.  There- 
fore, from  Colorado  to  Mexico,  there  are  many  irrigated  sections 
and  numerous  thriving  towns  and  cities.  The  only  large  tributary 
is  the  Rio  Pecos,  which  resembles  the  main  river. 

Owing  to  the  openness  of  parts  of  its  valley,  and  the  sandy 
nature  of  its  bed,  the  Rio  Grande  loses  much  of  its  volume  in 
crossing  the  arid  country  and  is  sometimes  dry  in  summer,  But 
in  winter  and  spring  it  is  a  large  river,  rising  especially  high 
during  the  melting  of  the  mountain  snows.  It  is  always  heavily 
charged  with  sediment,  and  in  places  is  aggrading  its  valley.  At 
its  mouth  a  delta  is  being  built,  causing  a  slight  bulge  in  the 
coast  line  (Fig.  371).  In  its  lower  portion  the  Rio  Grande  is 
navigable  to  small  boats ;  but  at  present  this  is  of  little  use,  since 
that  region  is  arid  and  sparsely  settled. 

Summary.  —  TJie  Rio  Grande,  siqjplied  ivith  ivater  from  the 
Rocky  Mountains,  Jloius  across  an  arid  region  to  the  sea,  receiv- 
ing only  one  large  tributary,  the  Pecos.  Its  course  is  marked  by 
alternate  canyons  and  open  valleys,  which  are  irrigated  and  well 
settled. 

206.  The  Mississippi  System.  —  This  vast  river  system, 
the  longest  and  one  of  the  largest  in  the  world,  has  a  length, 
including  the  Missouri,  of  4300  miles  and  a  drainage  area 
of  1,250,000  square  miles.  It  receives  a  large  number  of 
tributaries,  some  very  long,  including  the  Red  (1200  miles 
long),  Arkansas  (2170  miles),  Missouri  (3000  miles),  and 
Ohio  (975  miles).  Each  of  these  tributaries  has  large 
feeders,  some  of  them  great  rivers;  for  example,  the  Platte 
(900  miles)  and  the  Yellowstone  (1100  miles)  are  tributaries 
of  the  Missouri.  There  are  over  10,000  miles  of  navigable 
water  in  the  Mississippi  system  (Fig.  481). 

The  Mississippi  valley  is  a  broad  depression,  a  lowland  left 
by  the  greater  uplift  of  the  land  on  either  side.  Most  of  the 
streams  follow  consequent  courses  down  the  slopes  of  these  up- 
lifted sides.     This  depression  has  existed  for  many  ages,  at  first 


326 


NEW  PHYSICAL   GEOGRAPHY. 


Navigable  Interior  Water  Routes 

in  wliicli  tlie  water  is 

three  feet  (Jeep  or  over 

0   liK)        31111 


as  an  interior  sea,  into  which  sediment  was  brought  by  streams 
from  the  neighboring  highlands;  later  it  was  transformed  by 
uplift  to  dry  land  plains. 

As  a  whole,  the  Mississippi  valley  may  be  considered  a 
mature  valley,  approaching  old  age  in  its  lower  parts  and 
youth  in  its  upper  tributaries,  where  recent  changes  have 

rejuvenated  the 
streams.  The  re- 
juvenation has 
caused  many  can  - 
yons,  in  which 
there  are  falls,  like 
the  Great  Falls  of 
the  Missouri.  One 
of  the  most  noted 
canyons  is  that  of 
the  Yellowstone,  at 
the  head  of  which 
are  Yellowstone 
Falls  (Fig.  480), 
located  in  the  lava  plateau  of  Yellowstone  National  Park.  In 
many  places  volcanic  accidents  and  mountain  uplift  have 
rejuvenated  the  mountain  tributaries.  There  are  numerous 
instances  where  the  rivers  cut  across  mountain  ranges ;  for 
example,  the  Missouri  in  Montana,  and  the  Arkansas  in 
Colorado,  forming  the  famous  Royal  Gorge  of  the  Arkansas. 

Like  the  Colorado  and  Kio  Grande,  the  western  tributaries  are 
supplied  with  abundant  water  from  the  mountains,  especially  in 
spring,  when  they  become  20  or  30  times  as  high  as  at  the 
low  water  stage  of  autumn.  Only  about  one  ninth  of  the  rainfall 
is  carried  across  the  arid  plains,  so  much  are  the  streams  reduced 
by  evaporation.  This  water  is  of  great  value  for  irrigation,  and, 
by  storage,  will  make  the  plains  still  more  valuable. 

So  much  sediment  is  supplied  to  these  rivers,  and  so  much  water 
for  carrying  it  is  lost  by  evaporation  and  seepage,  that  the  streams 


BORMAY    4    CO. J    N.V. 

Fig.  481.  — Sketch  map  showing  (by  heavy  lines)  the 
navigable  rivers  of  United  States. 


mVERS   OF  UNITED   STATES,  32? 

are  all  muddy.  The  Platte  is  so  burdened  that  it  is  aggrading  its 
bed,  and  doing  it  with  such  rapidity  that  the  river  is  embarrassed 
in  passing  through  its  own  deposits  (Fig.  112).  The  Red  Eiver 
receives  its  name  from  the  color  of  its  sediment;  and  the  turbid 
Missouri  is  often  called  the  "Big  Muddy.''  At  their  junction,  the 
Mississippi  has  about  as  much  water  as  the  Missouri ;  but  since 
it  has  less  sediment,  it  is  able  to  move  down  stream  that  which  the 
Missouri  brings. 

The  Ohio  drains  part  of  the  Alleghany  plateau  on  one 
side  and  of  the  Central  Plains  on  the  other.  Since  the  cli- 
mate of  its  valley  is  humid,  with  a  rainfall  of  over  40  inches 
a  year,  the  Ohio  carries  more  water  than  the  Missouri. 
The  water  supply  varies  greatly,  being  least  during  summer 
droughts,  when  the  river  may  be  only  2  or  3  feet  deep,  and 
most  in  spring  when  the  snows  are  melting.  It  may  then 
reach  a  depth  of  from  50  to  60  feet  (Fig.  99). 

The  Ohio  and  most  of  its  tributaries  occupy  mature  val- 
leys; but  those  in  the  plateau  are  deep  and  steep-sided, 
dissecting  the  plateau  into  the  rugged  condition  of  early  ma- 
turity (p.  84).  Throughout  most  of  its  course  the  Ohio  is 
bordered  by  a  floodplain,  behind  which  bluffs  rise  to  a  height 
of  200  or  300  feet.  This  is  an  excellent  farming  country,  and 
the  valley  is  easily  followed  by  railways.  The  river  is  navi- 
gable even  above  Pittsburg,  though  in  some  places  rapids 
have  made  canals  necessary. 

The  upper  Mississippi  resembles  the  Ohio  in  most  impor- 
tant respects.  In  both  cases  the  valleys  have  been  seriously 
influenced  by  the  glacier,  which  has  caused  rapids  and  falls. 
In  its  headwaters,  the  Mississippi  passes  through  a  series 
of  lakes  and  swamps  of  glacial  origin. 

Below^  the  junction  of  the  Mississippi  and  Ohio  at  Cairo, 
the  Mississippi  flows  in  a  floodplain  which  it  is  building  up 
because  it  has  more  sediment  than  it  can  carry  down  the 
gentle  grade.  This  floodplain,  bordered  by  low  bluffs,  is 
^bout  600  miles  long  and  from  20  to  75  miles  wide.     Mem- 


828  NEW  PHYSICAL  OEOORAPHT. 

phis  and  Vicksburg  are  situated  on  the  eastern  blufp,  at 
points  where  the  river  swings  against  it.  Over  this  im- 
mense, fertile  floodplain  the  river  swings  in  a  series  of  mean- 
ders, often  as  much  as  5  miles  in  diameter.  These  nearly 
double  the  length  of  the  lower  river. 

The  river  is  slowly  changing  its  position  in  the  floodplain,  and, 
now  and  then,  the  neck  of  a  meander  is  cut  off  and  a  ring-shaped 
ox-bow  lake  is  left.  There  are  many  such  lakes  which  are  slowly 
being  filled  with  sediment.  Floods,  seepage  from  the  river,  and 
lack  of  drainage  on  the  level  floodplain  cause  the  abandoned 
channels,  or  bayous,  and  other  low  places,  to  remain  either  as 
lakes  or  swamps  (Fig.  308  ) ;  the  higher  parts  are  drier  and  make 
excellent  farm  land.  At  times  of  great  flood,  when  the  river 
may  rise  from  30  to  50  feet,  the  water  sometimes  opens  gaps,  or 
crevasses,  in  the  levees  which  men  have  built  to  confine  the  river. 
Then  the  water  tears  away  the  levees,  spreading  over  the  flood- 
plain  and  doing  great  damage.  It  is  the  deposits  made  during 
such  inundations  that  are  building  up  the  floodplain. 

Sediment,  washed  from  the  slopes  of  the  entire  Mississippi 
system,  has  built  a  large  delta  at  its  mouth  (Fig.  105).  This 
is  still  growing  outward,  for  each  year  enough  sediment  is 
poured  into  the  Gulf  to  build  a  pyramid  a  mile  square  at  the 
base  and  268  feet  high.  Most  of  the  delta  is  too  low,  level,  and 
marshy  for  habitation,  and  over  it  the  river  flows  sluggishly 
through  a  series  of  distributaries.  Sediment  is  constantly 
being  deposited  on  the  river  bed,  interfering  with  navigation, 
especially  at  the  river  mouth.  To  check  this,  jetties,  or  piers 
have  been  built  at  one  of  th^  mouths,  or  passes,  in  order  to 
confine  the  current  and  cause  it  to  flow  rapidly  enough  to 
keep  tlie  channel  open  for  large  vessels. 

Summary.  —  The  Mississippi,  with  its  many  large  tributaries,  occu- 
pies a  valley  left  as  a  lowland  by  the  greater  uplift  of  the  sides.  It 
is,  on  the  whole,  mature ;  but  rejuvenation,  by  volcanic  action  and 
by  ujdift,  has  occurred  in  many  of  its  headwaters.  The  tributaries 
which  cross  the  arid  westeryi  pjlaiiis  are  supplied  with  water  from 


RIVERS  Oj^    united  STATES,  329 

tJie  mountains,  whicJi  is  of  value  for  irrigation;  they  bring  much  sedi- 
ment. The  Ohio  and  upj)er  Mississippi  valleys  are  mature,  have 
abundant  rainfall,  and  are  excellent  agricultural  regions.  They  have 
been  affected  by  glaciation.  Below  Cairo  is  'a  broad  Jloodplain, 
betiveen  bluffs,  and  farther  down  a  delta,  both  made  of  sediment 
brought  by  the  river,     WJiere  dry  enough,  both  are  excellent  farm  land. 

207.  Smaller  Streams  of  the  East.  —  From  the  Kio  Grande  to 
northern  Maine  there  are  a  large  number  of  small  streams,  includ- 
ing the  Colorado  and  Brazos  of  Texas,  the  Alabama,  James,  Poto- 
mac, Susquehanna,  Delaware,  Hudson,  and  Connecticut.  South 
of  the  Hudson  their  lower  courses  are  across  the  coastal  plains, 
in  shallow  valleys  consequent  on  the  slope  of  the  plains.  Sink- 
ing of  the  land  has  made  most  of  the  larger  streams  navigable 
in  their  lower  courses.  In  some  cases,  especially  in  the  North, 
where  sinking  of  the  land  has  been  greatest,  vessels  can  pass  far 
inland.  The  importance  of  this  is  well  illustrated  by  the  Chesa- 
peake, Delaware,  and  Hudson  valleys. 

From  Alabama  northward  the  headwaters  of  the  large  streams 
are  either  in  or  west  of  the  mountains.  This  fact  has  been  of 
great  importance  in  many  cases,  since  it  has  opened  water  gaps 
into  and  across  the  mountains  (pp.  309  and  391).  North  of  New 
Jersey  the  streams  have  all  been  rejuvenated  by  the  effects  of  the 
glacier,  and  their  courses  obstructed  in  places  by  rapids,  falls,  and 
lakes,  the  importance  of  which  has  already  been  pointed  out. 

Summary.  — As  a  result  of  sinking  of  the  land,  'many  of  the  small 
streams  of  the  East  are  navigable  in  their  lower  courses  ;  some  fur- 
nish openings  into  and  across  the  Appalachians  ;  aiid  in  the  Northj 
glaciatioyi  has  caused  many  rapids,  falls,  and  lakes. 

208.  The  St.  Lawrence  System^ — This  remarkable  river 
system  includes  five  of  the  largest  eight  fresh-water  lakes  in 
the  world  (p.  162).  These  are  connected  by  short  rivers  and 
straits,  in  several  cases  containing  rapids  or  falls,  including 
the  wonderful  Niagara.  The  lake  basins  are  very  deep  (p.  161), 
the  bottoms  of  all  but  Erie  being  below  sea  level. 

The  St.  Lawrence  flows  out  of  Lake  Ontario,  not  in  a  well- 


330  yEW  PHYSICAL   GEOGRAPHY, 

defined  valley,  but  straggling  over  a  low,  hilly  land,  the  higher 
parts  of  which  rise  above  the  water  as  the  so-called  Thousand 
Islands.  From  tliis  point  down  to  Montreal  the  river  consists 
of  a  series  of  broad,  lake-like  expanses,  with  intervening  rap- 
ids around  which  canals  have  been  built.  The  lowest,  or  the 
Lachine  Rapids,  are  just  above  Montreal ;  and  thence,  onward 
to  the  sea,  there  is  uninterrupted  navigation  through  a  broad 
valley,  into  which  the  tide  has  been  admitted  by  sinking  of 
the  land.  Below  Quebec  the  valley  is  a  broad  bay,  and  ocean 
steamers  ascend  to  Montreal.  By  means  of  canals  around 
the  rapids  and  falls,  large  ships  may  go  on  to  the  western 
end  of  Lake  Superior  (p.  311). 

The  exact  preglacial  condition  of  the  St.  Lawrence  system  is 
not  yet  fully  known.  It  is  certainly  drowned  at  one  end,  and  the 
continuation  of  its  valley,  between  Nova  Scotia  and  Newfoundland, 
may  still  be  traced  on  the  sea  bottom.  When  this  submerged  val- 
ley was  formed,  northeastern  North  America  was  more  than  1000 
feet  higher  than  now,  and  the  mouth  of  the  St.  Lawrence  was  off 
Newfoundland  at  the  edge  of  the  continental  shelf. 

The  inland  continuation  of  this  valley  seems  to  have  been  not  the 
present  St.  Lawrence,  but  Ottawa  River,  the  only  large  tributary 
of  the  St.  Lawrence  system.  Above  Montreal  the  system  appears 
to  be  made  of  parts  of  several  systems,  united  by  the  effects  of 
glacial  erosion,  dams  of  glacial  drift,  and  land  tilting.  These 
processes  have  also  transformed  parts  of  the  valleys  into  the 
deep,  boat-shaped  basins  of  the  Great  Lakes  (p.  161).  Neither 
the  St.  Lawrence  above  Montreal,  nor  the  rivers  and  straits  that 
connect  the  lakes,  are  in  preglacial  valleys  of  large  streams. 

Notwithstanding  the  great  volume  of  water,  little  erosion 
is  being  done  along  most  of  the  St.  Lawrence.  The  expla^ 
nation  of  this  is  that  the  lakes,  and  other  quiet  stretches,  rob 
the  water  of  its  sediment,  therefore  taking  away  its  erosivo 
power.  Consequently,  though  young,  most  of  the  St.  Law- 
rence streams  flow,  not  in  gorges,  but  in  shallow  valleys. 

Niagara  River,  which  furnishes  the  one  striking  exception 


TilTERS  OF  UNITED  STATES.  331 

to  this,  has  peculiar  conditions.  Leaving  Lake  Erie  clear  and 
free  from  sediment,  the  broad  Niagara  loiters  along  past  Buf- 
falo, almost  on  the  surface  of  the  plain  (Fig.  483).  At  only- 
one  point  in  its  upper  course  is  there  rapid  water,  where  it 
crosses  a  ledge  of  rock  near  Buffalo.  The  river  divides  into 
two  channels  around  the  low  Grand  Island.  The  valley  is  so 
young  and  undeveloped  that  the  channel  on  one  side  has  not 
been  deepened  enough  to  rob  the  other  of  its  water. 

Just  above  Niagara  Falls,  15  miles  from  Lake  Erie,  the 
stream  is  again  divided,  this  time  around  Goat  Island.  Here 
the  flow  in  each  branch  quickens,  and  soon  the  water  is  tum- 
bling along  tumultuously  as  a  series  of  violent  rapids.  Then 
it  drops  as  a  great  cataract,  160  feet  high,  divided  by  Goat 
Island  into  two  parts,  —  the  larger,  or  Horseshoe  Fall,  on  the 
Canadian  side,  the  smaller,  or  American  Fall,  on  the  Ameri- 
can side.  For  7  miles  below  the  cataract  the  river  rushes 
rapidly  through  a  gorge  200  or  more  feet  deep,  and  200  or 
300  yards  wide  (Fig.  485).  In  two  parts  of  the  gorge  there 
are  decided  rapids,  and  at  one  point  a  whirlpool. 

The  top  of  the  gorge  is  at  the  level  of  the  plain  over  which 
the  river  flows  from  Buffalo  to  the  Falls;  and  the  gorge  cut 
in  this  plain  reveals  its  rock  structure.  It  is  made  of  nearly 
horizontal  strata,  some  hard,  some  soft,  dipping  gently  south- 
ward at  the  rate  of  about  35  feet  a  mile.  The  upper  stratum 
in  the  gorge  wall  is  massive  limestone  (Fig.  482),  beneath 
which  is  a  series  of  weak  shales.  It  is  these  strata,  also 
present  under  the  cataract,  that  make  the  waterfall  possible. 

The  plain  ends  toward  the  north  in  a  steep  slope,  or  escarp- 
ment (Fig.  485),  faced  by  a  plain  about  200  feet  lower. 
Emerging  from  its  gorge  at  this  escarpment,  the  river  flows 
quietly  over  the  lower  plain  to  Lake  Ontario. 

An  enormous  quantity  of  water,  estimated  at  167,000,000 
gallons  a  minute,  falls  over  the  Niagara  limestone  (Fig. 
482),  which  forms  the  crest  of  the  Falls.  The  underlying 
shales  are  being   removed  by   the  swirl  of   waters,  and  by 


332 


NEW  PHYSICAL  GEOGRAPKT, 


CUNTON   FOBMATION 


'^1 


MEDINA 


FORMATION 


the  grinding  against  them  of  great  blocks  of  fallen  limestone 
by  a  kind  of  pot-hole  action  (p.  54).  This  undermines 
the  limestone,  causing  huge  blocks  to  occasionally  break  off, 

slowly  changing 
the  outline  of  the 
cataract. 

There  is  too  lit- 
tle water  in  the 
American  Fall  for 
such  results ;  in- 
stead, the  fallen 
blocks  of  lime- 
stone protect  this 
fall  from  reces- 
sion. Records  kept 
since  1842  show 
that,  while  the 
Horseshoe  Fall 
has  receded  at  the 
rate  of  about  five 
feet  a  year,  the 
outline  of  the 
American  Fall  has  scarcely  changed.  Long  before  the  cata- 
ract has  receded  to  Lake  Erie,  the  southward  dip  of  the  shales 
will  have  carried  them  so  far  into  the  ground  that  there  will 
no  longer  be  an  opportunity  for  the  river  to  undermine  the 
limestone.     Then  the  waterfall  will  disappear. 

There  is  clear  evidence  that  when  the  ice  sheet  permitted 
Lake  Erie  to  outflow  over  the  plain  toward  Ontario,  the  Niagara 
cataract  was  born,  falling  over  the  edge  of  the  escarpment.  Since 
then  the  cataract  has  receded  for  seven  miles,  making  the  gorge. 
When  the  cutting  of  the  gorge  first  began,  the  river  occupied  a 
broad  valley  on  the  upper  plain,  similar  to  the  present  valley 
above  Goat  Island.  The  river  gravels  and  banks  made  at  that 
time  may  still  be  clearly  seen  on  the  plain,   200  feet  or  more 


Fig.  482.  — To  illustrate  the  undercutting  in  progress 
at  Niagara  (modification  of  Gilbert's  diagram). 


Fig.  483.  —  Bird's-eye  view  of  Niagara  River.     Contrast  the  broad,  shallow 
upper  valley  with  the  narrow,  deep  gorge  below  the  falls. 


"!      '  ■'1*!. 


^    t^'y>f^t-BSM,  > 


Fig.  484.  —  The  water  escaoing  here  is  a  small  portion  of  that  used  for  power 
at  Tfiagara  Falls.  Yet  only  a  very  minute  portion  of  the  enormous  power 
available  is  now  used. 


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RIVERS  OF  UNITED  STATES,  338 

above  the  present  river.  The  gorge  could  not  have  existed  then. 
Another  proof  that  the  gorge  has  been  cut  by  river  action  is  the 
existence  of  an  abandoned  fall,  similar  to  the  American  Fall,  at 
Foster  Flats,  more  than  halfway  down  the  gorge. 

As  the  cataract  receded,  it  discovered  a  buried  valley  beneath 
the  glacial  drift ;  and  where  this  buried  valley  leaves  the  gorge, 
at  the  whirlpool,  there  is  a  break  in  the  otherwise  continuous 
rock  wall  of  the  gorge.  The  removal  of  the  glacial  drift  that 
filled  this  buried  valley  has  formed  the  elbow  in  which  the  whirl- 
pool is  situated  (Fig.  485). 

It  was  formerly  thought  that  Niagara  gave  a  basis  for 
telling  the  time  in  years  since  the  close  of  the  Glacial  Period. 
Three  important  facts  are  known:  (1)  the  length  of  the 
gorge  ;  (2)  the  present  rate  of  retreat  of  the  cataract  (five 
feet  a  year) ;  (3)  the  cataract  began  as  the  ice  was  leaving. 
It  therefore  seemed  simple  to  divide  the  distance  by  the 
present  rate;  but  later  studies  show  that  there  are  many 
causes  for  variation  in  the  rate  of  retreat,  of  which  the  fol- 
lowing are  most  important :  (1)  the  limestone  is  thinner 
at  the  northern  end ;  (2)  the  time  required  to  remove  the 
loose  drift  in  the  buried  gorge  is  unknown;  (3)  the  volume 
of  water  has  varied ;  indeed,  at  one  time  Niagara  received 
the  waters  of  Lake  Erie  only  (Figs.  280,  281).  Since  it  is 
impossible  to  tell  just  how  much  these  variations  have  in- 
fluenced the  rate  of  retreat,  the  time  that  Niagara  has  taken 
to  cut  its  gorge  is  not  known  positively ;  but  there  is  reason 
for  believing  it  to  have  been  between  5000  and  10,000  years. 

Summary.  —  Tlie  St.  Lawrence  system  is  an  immature  river 
system  made  by  the  union,  largely  through  glacial  action,  of  parts 
of  a  number  of  rivers.  It  consists  of  (1)  a  drowned  lower  portion; 
(2)  a  middle  section  with  a  series  of  quiet,  lake-like  stretches  arid  inter- 
vening rapids;  arid  (3)  an  upper  portion  of  great  lakes,  ivith  connect- 
trig  straits  and  rivers,  interrupted  by  rapids  and  falls.  Little  erosion 
is  being  accomplished  because  the  lakes  rob  the  water  of  sediment  for 
cutting-tools.    Niagara  is  an  exception  to  this  because  of  the  existence 


334  NEW  PHYSICAL   GEOGRAPHY, 

of  weak  shales  beneath  a  massive  limestone.  At  the  Horseshoe  Fall 
the  removal  of  these  shales  is  causing  the  cataract  to  retreat  upstream^ 
and  there  is  good  jrroof  that  it  has  receded  through  the  seven  miles 
of  the  gorge,  requiring  probably  someivhere  between  5000  and  10,000 
years  for  the  work,  which  began  at  the  close  of  the  Glacial  Period. 

Topical  Outline  and  Review  Questions. 

Topical  Outline.  —  201.  The  Columbia.  —  Climate  ;  length  ;  area ; 
two  large  branches ;  valleys  in  lava  plateau ;  effect  of  these  canyons ; 
lower  valley,  —  crossing  mountains,  navigation,  fishing. 

202.  The  Sacramento.  —  Position  ;  outlet ;  size  ;  large  tributaries  ; 
navigation  ;  small  mountain  tributaries ;  uses  of  water. 

203.  The  Colorado.  —  Source  of  water;  size ;  inclosing  plateau  ;  canyon 
valleys;  lower  course  ;  Grand  Canyon,  —  barrier,  difficulties  of  passage, 
rapids,  canyon  walls  ;  tributaries  ;  young  plateau. 

204.  The  Great  Basin.  —  Area ;  situation  ;  minor  basins ;  Basin 
Ranges ;  rainfall ;  streams  ;  irrigation  ;  former  lakes. 

205.  The  Rio  Grande.  —  Compare  with  Colorado ;  irrigation ;  tribu- 
taries ;  variation  in  volume  ;    sediment  load ;  delta  ;  navigation. 

206.  The  Mississippi  System.  —  (a)  The  system :  length;  area;  prin- 
cipal tributaries ;  navigation.  (b)  The  valley :  origin  of  lowland ; 
ancient  sea;  mature  condition;  rejuvenation;  mountain  gorges. 
(c)  Western  tributaries:  water  supply;  floods;  loss  of  water;  irriga- 
tion; sediment,  —  cause,  Platte,  Red,  Missouri.  (d)  Ohio:  rainfall; 
floods;  mature  valley;  floodplains ;  farming;  navigation,  (e)  Glacial 
influence :  rapids  and  falls ;  upper  Mississippi,  (f )  Floodplain  of  lower 
Mississippi:  cause;  area;  bluffs;  meanders;  changes  in  river  position; 
lakes,  bayous,  and  swamps;  floods;  levees;  deposits,  (g)  Delta:  out- 
ward growth ;  swampy  surface  ;  distributaries ;  jetties ;  passes. 

207.  Smaller  Streams  of  the  East.  —  Names  of  principal  ones  ;  condi- 
tion on  Coastal  Plain;  effect  of  land  sinking;  pathways  across  moun- 
tains ;  effects  of  glacier. 

208.  The  St.  Lawrence  System.  —  (a)  Description :  lakes ;  connection 
of  lakes;  Thousand  Islands;  rapids  below  the  lakes;  drowned  lower 
course  ;  navigation,  (b)  Preglacial  condition  :  submerged  valley  ;  former 
elevation  of  continent ;  Ottawa  River ;  effect  of  glacier  on  river;  on  lakes. 
(c)  Erosion  :  absence  of  sediment ;  effect  on  valley  form,  (d)  Niagara  : 
near  Buffalo;  Grand  Island;  Goat  Island;  rapids;  two  falls;  gorge; 
upper  plain ;  rocks  in  gorge  wall ;  escarpment ;  condition  below  escarp- 
ment, (e)  Recession  of  falls :  cause  of  retreat;  condition  in  American 
Fall ;  rate  in  Horseshoe  Fall ;  future  of  falls,     (f )  History  of  Niagara : 


RIVERS  OF  UNITED   STATES.  335 

birth   of   falls;    cause   of   gorge;  proofs   of   this;    cause   of   whirlpool, 
(g)  Age  of  gorge :  facts  known;  causes  for  variation;  probable  age. 

Review  Questions.  —  201.  What  is  the  situation  of  the  Columbia? 
Its  length  and  drainage  area?  AVhat  are  the  two  great  branches? 
What  is  the  condition  in  the  upper  part  ?     In  the  lower  part  ? 

202.  Describe  the  Sacramento  Valley ;  its  situation ;  lower  portion  ; 
size  ;  large  branches  ;  small  tributaries  ;  uses  of  water. 

203.  State  the  general  features  of  the  Colorado  :  source  of  water ; 
size  ;  canyons  ;  lower  portion.  Describe  the  Grand  Canyon.  Why  are 
there  few  tributaries?     What  is  the  condition  between  them? 

204.  What  are  the  surface  features  of  the  Great  Basin  ?  What  is  the 
climate?    What  effects  has  this  on  the  region ? 

205.  Compare  the  Rio  Grande  with  the  Colorado.  How  do  they 
differ?  Why  is  there  so  much  irrigation?  How  does  the  volume  vary? 
What  is  the  condition  in  the  lower  course  ? 

206.  What  is  the  size  of  the  Mississippi  and  its  largest  tributaries? 
What  is  the  origin  and  form  of  its  valley  ?  What  is  the  condition  in  the 
headwaters?  What  is  the  condition  of  the  water  supply  in  the  western 
tributaries?  Of  the  sediment?  What  are  the  principal  characteristics 
of  the  Ohio?  What  effects  have  been  produced  by  glaciation?  What 
are  the  cliaracteristics  of  the  floodplain :  area  ;  bluffs  ;  meanders ;  floods ; 
swamps  ;  farm  land  ;  levees?     What  is  the  condition  on  the  delta? 

207.  Name  the  principal  small  streams  in  the  East.  What  are  their 
main  characteristics?     In  what  ways  are  they  important? 

208.  What  is  the  general  condition  of  the  system  ?  What  is  the  con- 
dition below  Lake  Ontario  ?  What  was  the  preglacial  condition  ?  Why 
is  there  little  erosion?  Describe  Niagara  River.  What  is  the  rock 
structure  of  the  gorge  walls?  How,  and  at  what  rate,  is  the  cataract 
caused  to  recede?  What  will  happen  as  the  fall  recedes  farther  ?  What 
proofs  are  there  that  the  gorge  was  formed  by  the  river?  Explain  the 
whirlpool.     What  is  known  of  the  length  of  postglacial  time  ? 

Reference  Books.  —  Gilbert,  Niagara  Falls,  National  Geographic  Mono- 
graphs, American  Book  Co.,  New  York,  1895,  $2.50  ;  Tarr,  Chapters 
VII,  VIII,  and  IX,  Phijsical  Geography  of  New  York  State,  Macmillan 
Co.,  New  York,  1902,  |3.50 ;  Dryer,  Studies  in  Indiana  Geography, 
Inland  Printing  Co.,  Terre  Haute,  Ind.,  1"897,  ^11.25 ;  Powell,  Exploration 
of  the  Colorado  River,  Washington,  1875  (out  of  print)  ;  Canyons  of  the 
Colorado,  Flood  and  Vincent,  Meadville,  Pa.,  1895,  $10.00;  Dutton, 
History  of  the  Grand  Canyon  District,  Monograph  II,  U.  S.  Geological 
Survey,  $10.00;  Grabau,  Niagara  Falls  and  Vicinity,  Bull.  45,  New 
York  State  Museum,  Albany,  1901,  $0.65, 


CHAPTER   XVII. 

DISTRIBUTION   OF  PLANTS. 
CONDITIONS  INFLUENCING   PLANT  LIFE. 

209.  Importance  of  Air.  —  Without  air,  both  plants  and 
animals  die.  Carbon  dioxide  from  the  air  is  taken  into  plant 
cells  and  changed  to  carbon  and  oxygen,  the  carbon  being 
built  into  the  tissues.  A  large  portion  of  the  plant  tissue 
is  made  of  carbon,  supplied  mainly  by  the  air. 

Air  is  present  everywhere  on  the  earth's  surface,  even  in 
soil  and  water  (p.  180) ;  therefore,  as  far  as  this  vital  sub- 
stance is  concerned,  it  is  possible  for  plants  to  be  present  on 
every  part  of  the  eartli's  surface.  The  fact  that  there  are 
some  places  where  plants  are  absent,  —  for  example,  under- 
ground, in  the  deep  sea,  and  in  central  Greenland,  —  is  proof 
that  there  are  other  things  of  vital  importance. 

Summary.  —  Air  is  of  vital  importance  to  plants,  supplying  most 
of  the  carbon,  of  which  a  large  part  of  plant  tissues  is  made. 

210.  Importance  of  Temperature.  —  Plant  activity  is  im- 
possible where  the  temperature  is  below  freezing,  for  then 
the  liquid  parts  are  frozen  and  cannot  move  about.  In  the 
ice-covered  interior  of  Greenland,  therefore,  where  the  tem- 
perature is  always  below  freezing,  all  plant  life  is  absent. 
Many  plants  are  not  injured  by  being  frozen  for  part  of  the 
year,  but  are  able  to  resume  growth  when  the  frost  is  gone. 

All  plants,  even  the  lowest  forms  of  bacteria,  are  killed 
when  subjected  for  a  short  time  to  temperatures  near  the 
boiling  point.  This  is  because  such  heat  causes  changes  in 
their  tissues  which  destroy  their  power  of  action. 

336 


Fig.  487.  —  Open  forest  of  the  East  late  in  the  fall.     Notice  how  short  the  lower 
limbs  have  become  because  of  the  lack  of  light  when  in  full  leaf. 


FlQ.  4tty.  —  X  Tiew  in  tha  forest  of  large  trees  m  western  Washington, 
growtii  of  ferOiS  drives  m  th«  lore»t  shades. 


A  rank 


,5^Cvj^ 


Fig, 


489.  —  Negro  woman  garden- 
ing in  the  tropical  zone. 


Fig.  490.  —  A  banana  tree  m  the  tropi- 
cal zone. 


—J 


.^^.^ 


Fig.  491.  —  A  view  of  the  savanna  of  Africa,  a  negro  village  in  the  foreground. 


Fig.  492.  —  A  banyan  tree,  in  tropical  In- 
dia, with  roots  descending  from  the 
lower  branches. 


Fig.  493.  —  A  cocoanut  palm. 


Fig.  494.  —  The  dense  tangle  of  the  tropical  forest.    The  opening  in  the  middle 
is  where  a  path  extends  through  the  forest. 


DISTRIBUTION   OF  PLANTS.  337 

A  low  form  of  plant  lives  on  the  lower  parts  of  the  Greenland 
glacier,  being  frozen  all  the  year  excepting  a  few  weeks  in 
summer,  when  it  lives  in  ice-cold  water.  Certain  lowly  plants 
thrive  in  the  hot  springs  of  Yellowstone  Park,  whose  water,  tliough 
hot  enough  to  destroy  most  plants,  is  not  up  to  the  boiling  point. 
These  instances  show  that  plants  may  become  adapted  to  very 
unfavorable  surroundings.  They  could  not  live  under  any  other 
conditions ;  yet  no  other  plants  could  live  where  they  do. 

Summary. — Even  the  loivest  plants  are  unable  to  live  where  the 
temperature  always  remains  below  freezing,  or  where  it  rises  to  the 
boiling  point  even  for  a  short  time;  but  many  survive  a  period  of 
freezing,  and  some  live  in  the  tvater  of  hot  springs. 

211.  Importance  of  Sunlight.  —  Sunlight  is  also  of  vital 
importance  to  plan-ts,  for  by  its  aid  the  green  cells  change 
carbon  dioxide  to  carbon  and  oxygen. .  The  branches  and 
leaves  of  plants  are,  therefore,  arranged  to  secure  air  and  sun- 
light ;  and  many  forest  trees  lose  their  lower  limbs  (Fig.  487), 
or  even  die  for  lack  of  light. 

Plants  growing  in  dark  places,  like  potatoes  sprouting  in  a  cellar, 
are  weak  and  tender,  and  their  lack  of  color  shows  the  absence 
of  the  important  chlorophyl  of  the  green  cells.  It  is  because  of 
absence  of  sunlight  that  no  plant  life  exists  on  the  ocean  bottom. 

Yet  some  low  plants  do  grow  in  darkness.  For  example,  a  weird- 
looking,  pale  white  fungus  lives  in  coal  mines  and  caverns,  where 
no  ray  of  sunlight  has  ever  entered.  This  is  another  instance  of 
how  life  may  adapt  itself  to  very  unfavorable  surroundings. 

Summary.  —  Light  is  needed  for  the  change  of  carbon  dioxide  to 
carbon  and  oxygen;  therefore  very  few  ploMts  live  in  dark  places. 

212.  Importance  of  Water.  —  No  plant  can  live  without 
water  ;  for  it  circulates  among  the  tissues,  bearing  food  and 
other  materials  from  one  portion  to  another,  as  man's  blood 
does.  In  trees  this  plant  blood  is  commonly  called  sap  ;  and 
when  it  rises  in  spring,  the  plant  awakens  from  its  long  winter 
sleep  and  bursts  into  leaf  and  flower. 


338  NEW  PHYSICAL   GEOGRAPHY. 

Plants  living  in  water  have  a  supply  ever  at  hand  ;  but  most 
land  plants  obtain  water  from  the  soil,  though  in  damp  tropical 
forests  some  species  secure  enough  from  the  air.  If  the  soil  dries, 
plants  wither ;  but  in  arid  and  desert  regions  plants  have  fitted 
themselves  to  survive  long  periods  of  drought. 

Summary. —  Water,  needed  for  the  sap  of  plants,  is  obtained  from 
the  neater,  air,  and  soil. 

213.  Importance  of  Soil.  —  Soil  is  not  necessary  to  plant 
life.  Water  plants,  both  fresh  and  salt,  may  secure  all 
necessary  substances  from  the  surrounding  water.  Thus 
many  float  freely  about,  while  others  have  roots  solely  for 
the  purpose  of  anchoring  themselves  in  place.  Some  land 
plants,  called  epiphytes^  are  also  able  to  live  without  roots, 
securing  all  necessary  substances  from  the  air.  The  great 
majority  of  land  plants,  however,  depend  on  the  soil  for  most 
of  their  water,  part  of  their  food,  and  for  anchorage. 

The  plant  food  in  the  soil  is  of  so  great  importance  that,  where 
it  is  almost  absent,  as  in  sand,  the  soil  is  called  sterile,  and  most 
species  of  plants  do  not  flourish.  Plants  remove  so  much  mineral 
matter  from  the  soil  that,  where  crops  are  raised  year  after  year,  it 
is  necessary  to  use  a  fertilizer  to  replenish  the  plant  food. 

Plants  are  adapted  to  different  kinds  of  soils,  some  needing 
loose,  open  soil,  others  compact,  clayey  soil ;  some  requiring  one 
kind  of  plant  food,  others  another.  A  very  little  study  of  wild 
flowers  or  crops  shows  that  plant  life  varies  with  the  soil. 

Summary.  —  Most  land  plants  depend  on  soil  for  ivater,  mineral 
food,  and  anchorage;  hut  some  land,  and  most  water  plants  do  not 
need  soil.     Land  plants  differ  greatly  according  to  the  soil. 

214.  Importance  of  Gravity.  —  Plants  send  their  roots  into  the 
ground,  seeking  water  which  gravity  has  drawn  into  the  earth. 
Seeking  sunlight,  they  send  their  stems  straight  up  from  the 
ground.  This  is  the  easiest  way  for  them  to  resist  the  pull  of 
gravity ;  if  they  were  inclined,  for  example,  they  would  fall  far 
more  easily.  To  aid  in  withstanding  the  pull  of  gravity  and 
the  force  of  the  wind,  large  plants  build  strong,  woody  trunks 


DISTRIBUTION  OF  PLANTS.  339 

and  branches.  Water  plants,  on  the  other  hand,  are  usually- 
weak,  loose-textured,  and  flabby,  because  they  live  in  a  denser 
medium,  which  buoys  them  up  so  that  they  do  not  need  great 
strength  to  resist  gravity.  Such  plants  as  sea  weeds,  which  are 
exposed  to  waves,  require  a  tougher  texture. 

Summary.  —  The  influence  of  gravity  causes  plants  to  send  roots 
downward,  and  strong,  woody  stems  straight  upward. 

DISTRIBUTION   OF  PLANTS. 

From  what  has  been  said,  it  is  evident  that  the  distribu- 
tion of  plants  is  influenced  by  surrounding  conditions  ;  and 
since  there  i&  much  difference  in  the  climate  and  soil  of  the 
earth,  there  are  great  differences  in  plant  life. 

215.  Influence  of  Climate.  —  Climate  is  the  greatest  factor 
in  determining  the  distribution  of  plants.  Some  species, 
especially  the  more  lowly,  have  a  wide  distribution  and  are 
adapted  to  many  climates ;  but  most  plants  of  higher  orders 
are  fitted  for  only  one  set  of  surroundings.  For  example, 
sugar  cane  requires  a  warm,  damp  climate  beyond  the  reach 
of  frost;  cotton  grows  best  in  a  slightly  cooler,  though  still 
warm,  sunny  climate;  corn,  though  requiring  a  long,  warm 
summer,  grows  much  farther  north  than  cotton ,  and  wheat 
may  be  raised  in  a  climate  too  cold  for  corn.  Wild  plants 
are  limited  in  distribution  in  similar  ways. 

There  are,  therefore,  zones  of  plant  life  similar  to  the 
zones  of  temperature.  An  Arctic  plant  will  die  amid  tropical 
heat  as  certainly  as  a  tropical  plant  will  perish  when  exposed 
to  the  frosts  of  a  temperate  winter.  The  plant  life,  or  flora^ 
of  moist  climates  also  differs  from  that  of  arid  climates. 
These  differences  may  be  best  understood  by  studying  the 
plant  life  in  several  climatic  zones. 

Summary. —  There  are  zones  of  plant  life,  similar  to  those  of  cli- 
mate ;  for,  while  some  lowly  plants  are  adapted  to  several  zones, 
higher  plants  are  usually  fitted  for  life  in  only  one. 


340  NEW  PHYSICAL   GEOGRAPHY, 

216.  Arctic  Flora.  —  In  the  Arc  tie,  plants  spring  up  as 
soon  as  the  frost  melts,  and  quickly  flower  and  bear  fruit, 
for  the  season  is  short.  Lichens  in  great  variety  cling  to  the 
rocks  (Fig.  486),  and  many  mosses  and  water-loving  plants 
live  in  the  swampy  soil.  There  are  grasses,  numerous  flower- 
ing plants,  and  species  with  woody  tissue,  including  dwarf 
willows  and  birches  —  true  trees  in  all  respects  but  size. 
They  cling  close  to  the  ground,  not  rising  high  because  it 
is  important  that  the  first  snows  shall  cover  and  protect 
them  from  the  cold  blasts  of  winter.  The  short  growing 
season,  and  the  bitter  winter  cold,  prohibit  the  growth  of  trees. 

For  more  than  two  thirds  of  the  year,  while  the  temperature 
is  below  the  freezing  point,  plant  life  is  dormant ;  bai  in  the  brief 
summer  season  the  sap  flows,  the  plants  grow,  pad  the  tundra 
is  covered  with  a  mat  of  green,  dotted  with  bits  of  color.  Yet 
only  the  surface  soil  is  free  from  ice,  for  at  depths  greater  than 
two  or  three  feet  frost  is  ever  present. 

Summary.  —  In  the  short  Arctic  summer,  ivhen  frost  melts  from 
the  iqjper  layers  of  soil,  ijlants  grow  rapidly,  clinging  close  to  the 
ground  to  secure  protection  from  the  winter  cold. 

217.  Temperate  Flora.  — Near  the  margin  of  the  temperate 
zone  in  both  hemispheres  is  a  timber  line  of  low,  scraggy  trees 
struggling  for  existence  amid  unfavorable  surroundings.  The 
trees  are  all  of  hardy  varieties,  some  evergreen^  others  decidu- 
ous^ that  is,  shedding  their  leaves  in  autumn.  The  evergreens 
have  tough,  needle-like  leaves  which  withstand  the  cold  of 
winter,  falling  only  in  spring,  when  new  ones  take  their 
place.  Among  the  common  evergreens  are  spruce,  hemlock, 
balsam,  fir,  and  pine. 

In  the  warmer  part  of  the  temperate  zone  deciduous  trees 
increase  in  number  and  variety,  including  the  beech,  birch, 
maple,  oak,  elm,  chestnut,  hickory,  ash,  walnut,  and  many 
otlier  species.  There  are  also  many  fruit  trees  such  as  apple, 
pear,  peach,  and  cherry.     These  trees,  which  spring  into  leaf 


DISTRIBUTION  OF  PLANTS.  341 

and  blossom  in  spring,  and  bear  fruit  in  summer  and  fall, 
are  checked  by  the  autumn  frosts.  Their  sap  then  ceases 
to  flow,  the  leaves  assume  brilliant  colors,  then  fall,  and  for  a 
time  the  trees  are  dormant-  They  lay  aside  their  activity 
during  the  season  when  active  life  is  impossible. 

Other  plants,  called  perennials,  die  down  to  the  ground 
when  the  frosts  come,  growing  again  in  spring  from  roots 
or  bulbs  in  which  nourishment  has  been  stored  during  the 
active  season.  Still  others,  called  annuals,  die  completely  in 
the  fall,  leaving  only  seeds  to  reproduce  their  species  when 
growth  is  again  possible. 

The  flora  of  the  temperate  zone  varies  greatly  according  to 
temperature,  exposure,  humidity,  and  soil.  There  are  places 
where  trees  do  not  grow,  for  example  on  dry  plains,  and  on 
prairies  (p.  77),  on  which,  however,  grasses  and  many  flower- 
ing plants  grow  luxuriantly.  In  other  places  tree  growth  is 
scrubby  and  of  few  kinds,  as  in  sandy  soils  which  support  only 
pines  and  oaks.  On  the  other  hand,  there  are  places  where 
the  climate  and  soil  favor  a  luxuriant  forest  growth.  Every 
part  of  the  land  is  occupied  to  its  fullest  extent  by  plants  fitted 
to  live  there. 

One  of  the  most  remarkable  instances  of  plant  growth  is  in  the 
region  of  "  big  trees  "  on  the  west  coast  of  United  States  (Fig.  488). 
There,  a  fertile  soil,  a  damp,  equable  climate,  and  absence  of  strong 
winds  encourage  the  growth  of  enormous  trees.  Only  in  south- 
eastern Australia,  where  similar  conditions  exist,  are  there  trees 
rivaling  these  in  size.  Some  of  the  California  trees  are  300  feet 
high,  40  feet  in  diameter,  and  fully  2000  years  old. 

Summary.  —  J^ear  the  frigid  zone,  tree  growth  ceases,  the  timber 
line  being  marked  by  scraggy  trees,  both  evergreen  and  deciduous. 
Deciduous  trees  increase  in  number  and  variety  in  the  ivarmer  parts 
of  the  temperate  zone.  Plants  are  adapted  to  the  winter  season  in 
several  ways :  by  suspendiiig  activity,  by  dying  doivn  to  the  ground, 
and  by  dying  completely,  leaving  seeds  to  continue  the  species, 
TJiere  are  many  differences  hi  flora  according  to  temperature,  ex- 
posure^  humidity,  and  soil. 


342  NEW    FSTSICAL    GEOGRAPHT. 

218.  Tropical  Flora.  In  the  warm,  humid  portions  of 
the  temperate  zones,  near  the  tropics,  the  abundant  and  varied 
flora  is  more  like  that  of  the  tropical  than  of  the  cool  temperate 
zone.  It  is  therefore  called  subtropical.  Both  here  and  in 
the  humid  tropical  zone  the  warmth  and  dampness  favor  the 
luxuriant  growth  of  a  great  variety  of  species.  Among  these 
are  long-leaved  pines,  broad-leaved  evergreens,  palmettoes, 
and  palms  (Figs.  493,  499)  ;  also  such  valuable  trees  as  the 
teak,  mahogany,  rosev/ood,  cocoa,  banana  (Fig.  490),  and  the 
rubber  tree. 

There  is  no  one  season  of  growth,  and  no  dormant  period; 
blossoms  may  appear  at  any  time^  and  there  is  no  period  when  all 
the  leaves  fall.  The  trees  grow  to  great  size,  and,  in  their  strug- 
gle for  light,  to  great  height.  The  undergrowth  is  dense  (Fig.  494), 
trailing  vines  hang  from  the  limbs,  and  epiphytes  abound. 

Summary.  —  The  suhtropical  flora  of  the  warm  temperate  zone 
and  the  tropical  flora  are  quite  alike  in  variety  and  luxuriance  of 
growth,  and  in  the  absence  of  a  dormarit  period. 

219.  Flora  of  Savannas  and  Steppes  (pp.  283,  285).  —  In  regions 
where  there  is  a  season  of  drought,  as  in  the  savannas  (Fig.  491) 
and  steppes,  trees  cannot  grow  excepting  along  the  streams.  Many 
grasses  and  flowering  plants  bridge  over  the  period  of  drought  by 
means  of  roots,  bulbs,  and  seeds,  springing  into  life  when  the  rains 
come,  as  plants  of  the  cool  temperate  zone  do  at  the  close  of 
winter.     Therefore,  such  regions  are  excellent  pasture  lands. 

Summary.  —  Regions  having  a  period  of  drought  are  treeless;  hut 
annuals  and  perennials  thrive,  making  these  good  pasture  lands. 

220.  Desert  Flora.  —  In  deserts  there  is  too  little  moisture 
for  a  great  number  of  individuals.  Therefore,  instead  of 
having  a  complete  cover  of  vegetation,  the  desert  is  scantily 
clothed  with  a  scattered  flora  (Figs.  154,  498).  Every  pos- 
sible effort  is  made  by  the  plants  to  secure  and  retain  enough 
moisture  for  life.  Some  plants  have  enormous  roots,  extend- 
ing deep  into  the  ground  and  spreading  far  about  in  search 


DISTRIBUTION  OF  PLANTS,  343 

of  water;  tlie  mesquite,  for  example,  lias  several  times  as 
much  woody  matter  below  ground  as  above  it.  Water  is 
stored  in  these  roots  for  use  during  the  long  droughts. 

Desert  plants  have  many  devices  for  existence  amid  their  un- 
favorable surroundings.  In  order  that  the  surface  for  evaporation 
may  be  reduced  to  a  minimum,  no  more  leaves  are  produced  than 
are  absolutely  necessary;  and  in  many  cases  the  leaves  are  small 
and  tough,  or  are  even  reduced  to  spines.  In  the  cacti  (Figs.  495- 
497),  which  are  especially  well  fitted  for  desert  life,  water  is 
stored  in  the  tissues  ;  there  are  no  true  leaves  ;  and  the  plant  has 
a  hard,  shiny,  varnished  surface,  through  which  evaporation  is 
almost  impossible.  Some  species  are  globular  in  form,  thus  ex- 
posing the  least  possible  surface  to  evaporation ;  and  the  sharp- 
irritating  spines  protect  them  from  many  kinds  of  animals  which 
might  otherwise  devour  them.  Many  desert  plants  repel  plant- 
eating  animals,  as  the  common  sage  brush  does,  w^liose  tough,  pale 
green  leaves  have  a  disagreeable  odor  and  taste. 

Sunlight,  temperature,  and  much  of  the  desert  soil  are  favor- 
able to  abundant  plant  life ;  but  water  is  lacking.  It  is  re- 
markable that  any  plants  should  be  able  to  adapt  themselves  to 
life  where  rain  comes  at  intervals  of  months  or  even  years.  That 
this  is  the  only  unfavorable  condition  is  proved  where  oases  exist 
in  the  desert,  or  where  irrigation  is  introduced.  Then  the  watered 
desert  supports  plant  life  in  great  variety  and  luxuriance. 

Summary.  —  Because  of  lack  of  water,  the  desert  flora  is  scattered 
and  many  devices  are  adopted  to  store  enough  ivater  to  last  through  the 
periods  of  drought.  TJie  luxuriance  of  growth  on  oases  and  irri- 
gated sections  proves  that  ivater  is  all  that  is  lacking  for  plant  life. 

221.  Mountain  Flora.  —  In  every  zone  the  flora  varies  with 
altitude.  A  temperate  flora  is  found  on  mountain  slopes  in 
the  tropical  zone;  and  an  Arctic  flora  on  mountain  tops  in 
temperate  zones.  Thus,  species  growing  in  Labrador  and 
Greenland  are  also  found  on  the  top  of  Mt.  Washington. 

Even  in  the  tropical  zone  there  is  a  line,  the  timber  line  (p.  96), 
above  which  it  is  too  cold  for  trees  to  grow.     This  line,  marked 


344  NEW  PHYSICAL    GEOGRAPHY. 

by  stunted,  scrubby  trees,  is  not  regular,  but  extends  highest 
on  those  slopes  which  furnish  most  protection  from  winds 
or  longer  exposure  to  the  sun  (Figs.  158,  161,  166).  Above  the 
timber  line,  wherever  there  is  soil,  the  surface  is  covered  with  low 
bushes  and  flowering  plants  (Fig.  181),  forming  the  mountain  or 
Alpine  flora,  famed  for  the  variety  and  beauty  of  its  flowers.  The 
cool  summer  air,  damp  soil,  and  long,  cold  winters  resemble  con- 
ditions in  the  Arctic ;  but  there  is  more  sunlight. 

Mountains  and  high  plateaus  rising  from  desert  lands  may 
have  rainfall  enough  for  forest  growth.  On  the  lower  slopes  the 
trees  are  stunted,  scrawny,  and  scattered,  showing  the  struggle 
with  drought;  but  higher  up  the  forest  becomes  dense.  If  the 
mountains  are  high,  tree  growth  may  be  checked  above  by  cold, 
as  well  as  below  by  drought. 

Summary.  — Because  of  changes  in  temperature,  the  flora  varies 
with  altitude.  On  mountain  slopes  the  forest  disappears,  and  in  the 
upper  portion  is  replaced  by  the  Alpine  flora. 

222.  Water  Plants.  —  Wherever  conditions  favor,  both  in 
salt  (p.  195)  and  fresh  water,  there  is  a  varied  flora,  some 
species  floating  on  the  surface,  others  anchored,  and  still  others 
having  true  roots.  Lower  forms,  such  as  algse  and  mosses, 
are  especially  adapted  to  life  in  water;  but  higher  forms,  even 
trees,  are  not  absent.  Rushes,  reeds,  mosses,  and  lilies  are 
among  the  common  fresh- water  and  swamp  plants;  and  among 
trees  the  cypress,  black  gum,  willow,  and  mangrove  are  com- 
mon, the  latter  living  in  salt  water  (Fig.  379). 

Most  trees  die  if  their  roots  are  submerged,  because  air  is 
cut  off;  but  water-loving  trees  have  special  provision  for  securing 
the  necessary  air.  For  example,  mangrove  roots  start  from  above 
the  water  surface,  and  even  from  the  lower  limbs ;  and  knobs,  or 
knees,  grow  upward  from  cypress  roots  till  they  project  above  the 
water  surface  (Fig.  307). 

Summary.  —  Plant  life  is  abundant  both  in  fresh  and  salt  ivater, 
the  lower  forms  being  especially  common,  though  even  some  trees 
are  adapted  to  life  in  water. 


Fig.  495.  —  The  prickly  pear,  one  of  the 
spiny  cacti. 


Fig.  496.  —  The  tree  Yucca  of  south- 
western United  States.  The  man 
on  the  right  gives  an  idea  of  the 
size  of  this  plant. 


fiQ.  497.  —  A  group  ol  cacti,  showing  rounded  forms  and  spiny  surface§. 


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DISTRIBUTION   OF  PLANTS.  345 

223.  Means  of  Distribution.  —  Since  the  land  is  so  well 
occupied  that  it  is  difficult  for  a  new  plant  to  gain  a  foot- 
hold, it  is  necessary  that  adequate  provision  be  made  to 
insure  the  spread  of  plants.  Seeds  are  the  principal  means 
of  insuring  this  spread.  It  is  necessary  to  produce  far 
more  seeds  than  can  possibly  find  a  chance  to  grow,  for  some 
are  eaten,  some  decay,  some  fall  where  they  cannot  sprout,  and 
some  that  sprout  find  conditions  so  unfavorable  that  they  die. 

In  order  that  they  may  have  every  chance  for  a  start  in  life, 
seeds  are  provided  with  many  ingenious  devices  to  aid  in  their 
spread.  Some  are  so  light  that  they  are  drifted  about  by  the 
slightest  breeze ;  some,  like  the  maple,  have  wing-like  projections 
that  catch  the  wind ;  some,  like  dandelion  seeds,  have  a  light, 
feathery  float;  some,  like  the  many  burs,  have  hooks  that  catch 
upon  the  fur  of  animais ;  and  some,  like  the  apple  or  peach,  are 
covered  with  an  edible  coat.  Animals  eat  these  fruits,  often  de- 
positing the  hard,  protected  seeds  far  away  from  the  parent  plant. 

The  wind  and  animals  are  the  two  agencies  most  important 
in  spreading  plants.  Because  light  seeds  are  so  easily  car- 
ried by  the  wind,  light-seeded  plants  are  most  widely  dis- 
tributed. Rivers  also  float  seeds  and  plants  from  one  place 
to  another,  and  ocean  currents  may  drift  them  even  to  oceanic 
islands.  Man  has  become  an  important  agent  in  distributing 
plants  over  the  earth.  He  carries  cultivated  plants  from  one 
region  to  another,  and  also  distributes  many  weeds.  In  this 
way  the  Canada  thistle  and  the  white  field  daisy,  now  com- 
mon weeds,  were  brought  to  the  United  States. 

Summary. — Plants  are  distributed  mainly  hy  seeds  ;  arid  since 
many  seeds  are  destroyed,  far  more  are  produced  than  coidd  possibly 
grow.  They  are  largely  distrihided  by  ivind  and  by  animals,  with  the 
aid  of  many  interestiyig  devices  ;  also  by  rivers,  ocean  currents,  and 
by  man.     Light-seeded  plants  are  most  easily  and  widely  distributed. 

224.  Barriers  to  the  Spread  of  Plants.  —  If  seeds  from  the 
land  fall  upon  water,  they  do  not  grow  unless  drifted  ashore. 


346  NEW  PHYSICAL   GEOGRAPHY. 

In  other  words,  water  is  a  barrier  to  their  spread ;  it  is,  in 
fact,  the  greatest  barrier  to  the  distribution  of  land  plants, 
especially  if  it  is  a  large  body  like  the  ocean.  It  would  be 
under  very  rare  conditions,  for  example,  that  even  a  single 
seed  could  be  carried  from  South  America  to  Africa  by  winds, 
currents,  or  birds. 

Yet  even  the  ocean  is  not  an  absolute  barrier,  and  plants 
from  the  mainland  are  found  on  all  oceanic  islands.  Only 
the  seeds  of  certain  plants  find  their  way  there,  however,  and 
island  floras  are,  therefore,  far  less  varied  than  those  of  the 
mainland.  The  most  common  plants  are  those  with  seeds 
so  light  that  they  are  easily  carried  by  wind ;  or  those  that 
birds  eat  and  carry;  or  those,  like  the  cocoanut,  that  will 
float  for  a  long  time  in  the  sea. 

Deserts  are  barriers  because  no  plants,  except  those  adapted  to 
desert  conditions,  can  spread  across  them,  unless  carried  entirely 
over.  A  tropical  forest  is  an  equally  good  barrier  for  plants 
that  are  adapted  to  desert  life.  Mountain  chains  are  also  barriers, 
because  plants  at  their  base  will  not  spread  into  the  cold  climates 
above ;  but  gaps  or  passes  often  are  pathways  for  the  spread  of 
plants  across  mountains.  The  wind,  although  an  aid  to  distribu- 
tion in  one  direction,  is  a  very  important  barrier  to  spread  in  the 
opposite  direction.  Tor  this  reason  European  plants  are  not  likely 
to  reach  America  against  the  west  winds ;  but  these  winds  aid 
American  plants  in  their  spread  to  Europe.  Ocean  currents  and 
birds  also  aid  in  the  same  direction. 

Summary.  —  The  ocean  is  the  greatest  harrier  to  the  spread  of 
land  x>lants  ;  hut  even  this  is  not  an  ah  solute  harrier,  for  plants 
ivhose  seeds  can  be  carried  hy  winds,  hirds,  and  ocean  currents  are 
found  even  on  reynote  oceanic  islayids.  Deserts  and  Tnountains  are 
also  harriers  ;  and  wind  checks  the  spread  of  plants  agaiiist  it. 

225.    Variation   in   Plants.  —  Among    plants    there    is    a 
struggle   for  air,  food,  light,  water,  and  opportunity  to  re 
produce  their  kind.     This  struggle  is  going  on  everywhere ; 
it  may  be  seen  in  a  neglected  flower  garden,  where  weeds 


DISTRIBUTION   OF  PLANTS.  347 

spring  up  from  chance  seeds,  and,  being  better  fitted  for  the 
struggle  than  carefully  nourished,  cultivated  plants,  take 
complete  possession  of  the  garden.  They  tower  above  the 
cultivated  plants,  shutting  out  light  and  robbing  the  roots  of 
water  and  mineral  food.  Under  such  conditions  the  culti- 
vated flowers  are  small  and  imperfect. 

Because  of  this  struggle  for  existence  plants  are  steadily 
changing;  and  those  that  best  fit  themselves  for  the  struggle 
have  the  best  chance  of  surviving  and  spreading.  This  has 
been  called  the  survival  of  the  fittest.  In  this  struggle  plants 
have  fitted  themselves  to  survive  the  cold  of  winter;  to  live 
amid  the  unfavorable  surroundings  of  the  desert;  in  fact,  to 
grow  among  most  conditions  on  the  earth's  surface.  Fossils 
in  the  rocks  prove  that  similar  change,  or  evolution^  has  been 
in  progress  for  ages. 

The  following  will  serve  as  illustrations  of  how  plants  are 
forced  to  vary  with  environment,  that  is,  to  undergo  evolution.  A 
mountain,  rising  above  the  timber  line  and  bearing  an  Alpine 
flora,  is  slowly  worn  down  to  the  low,  hilly  condition  of  maturity. 
If  the  plants  cannot  adapt  themselves  to  the  changes  in  climate, 
slope,  and  soil,  they  must  give  place  to  forms  better  fitted. 

The  effect  of  the  ice  sheet  offers  another  illustration.  As  it 
advanced  over  the  land,  it  either  drove  out  or  destroyed  all  life ; 
and  near  its  margin  the  climate  was  changed  from  warm  to  cold, 
so  that  the  plants  living  there  either  had  to  adapt  themselves  to 
the  changes  or  die.  When  the  glacier  melted  away  a  new  soil  was 
uncovered,  and  a  struggle  ensued  for  possession  of  it.  The  light- 
seeded  plants  came  first,  and  even  now  the  heavy-seeded  plants 
are  slowly  advancing  northward.  These  changing  conditions  have 
forced  some  species  to  evolve  new  characteristics.  The  history 
of  plant  life  during  past  ages  has  been  a  succession  of  changes 
by  which  plants  have  become  better  adapted  to  their  surroundings. 

Plants  undergo  many  changes  as  a  result  of  their  relation  to 
animals.  Since  animals  depend  on  plants  for  food,  some  means 
must  be  provided  to  prevent  complete  destruction.  For  this  pur- 
pose hard  wood,  thorns,  bitter  taste,  and  other  means  have  been 


348  NEW  PHYSICAL   GEOGRAPHY. 

evolved.  Many  plants  make  use  of  animals,  for  example,  in 
spreading  seeds  and  in  distributing  pollen.  Honey,  odor,  color, 
and  many  interesting  forms  of  flowers  are  provided  to  attract 
insects  and  to  secure  from  them  the  service  of  carrying  the 
pollen. 

Man  is  now  one  of  the  most  important  agents  in  chang- 
ing plants.  By  giving  them  better  care,  with  plenty  of  light 
and  food,  and  removing  weeds,  thus  relieving  them  from 
the  struggle  with  other  plants,  he  is  able  to  secure  far  larger 
seeds  and  fruits  than  grow  naturally.  For  example,  a  good 
apple  tree,  left  to  itself,  soon  has  to  struggle  with  weeds  and 
bushes,  and  its  fruit  becomes  sour  or  bitter.  By  much  care 
and  many  devices,  men  are  constantly  producing  new  varie- 
ties of  flowers  and  fruit.  This  is  done  by  forcing  evolution 
to  work  more  rapidly  than  it  does  naturally;  and,  in  this  way, 
changes  may  be  caused  in  a  few  years  which,  by  natural 
processes,  might  require  centuries. 

Summary.  —  The  struggle  of  plants  to  adapt  themselves  to  their 
svrroundings,  that  is,  the  struggle  for  existence,  which  is  every- 
where and  always  in  progress,  causes  iveaker  forms  to  die  out  and 
results  in  the  survival  of  the  fittest.  Slow  changes  in  climate  or  in 
land  form  cause  variation,  or  evolution,  in  plants.  Changes  are  also 
brought  about  for  the  purpose  of  protection  from,  or  making  use  of, 
animals  ;  and  man  is  noiv  causing  changes  at  a  far  more  rapid  rate 
than  evolution  naturally  icorks. 

226.  Plants  of  Value  to  Man.  —  Man,  like  other  members 
of  the  animal  kingdom,  depends  for  food  upon  plants.  Even 
though  he  may  feed  on  meat,  the  animal  from  which  it  came 
receives  nourishment,  directly  or  indirectly,  from  plants.  In 
a  warm  climate  so  great  an  abundance  of  plant  food  may  be 
easily  obtained,  at  all  seasons,  that  there  is  little  need  of 
special  provision.  But  in  climates  with  a  dry  or  cold  season 
it  is  highly  important  to  provide  a  store  of  food  for  use  dur- 
ing the  unfavorable  season.  This  need  has  led  to  the  culti- 
vation of  food  plants. 


DISTRIBUTION  OF  PLANTS,  349 

The  portions  of  plants  most  useful  for  food  are  those  in 
which  nourishment  has  been  stored  to  aid  in  the  propaga- 
tion of  the  species.  Among  these  are  seeds,  like  wheat ; 
fruits,  like  bananas  ;  bulbs,  like  onions ;  and  tubers,  like 
potatoes.  Some  of  the  food  plants,  like  dates,  cocoanuts, 
bread  fruit,  and  bananas,  used  extensively  in  warm  climates, 
have  been  changed  very  little. 

Others,  especially  those  cultivated  in  the  temperate  zones, 
have  been  so  improved  that  they  are  now  quite  unlike  the 
original  plants  which  savage  man  first  ate.  The  most  im- 
portant of  these,  including  the  orange,  apple,  pear,  peach, 
cherry,  grape,  wheat,  barley,  oats,  and  rye,  have  been  carried 
to  many  parts  of  the  world.  In  the  case  of  many,  the  source 
is  not  now  known ;  but  most  of  our  food  plants  apparently 
came  from  Asia,  where  they  have  been  cultivated  for  thou- 
sands of  years.  America  has  added  the  potato,  tomato, 
pumpkin,  and  Indian  corn,  or  maize,  as  well  as  tobacco. 

Plants  also  supply  us  with  materials  for  shelter,  clothing, 
medicine,  and  other  purposes.  Cotton  (Fig.  503)  is  the  most 
valuable  of  the  several  plant  libers  used  for  clothing.  In  all 
lands  wood  is  used  both  for  shelter  and  for  ornamental 
purposes.  Sugar  (Fig.  501),  coffee,  tea  (Fig.  502),  cocoa, 
vanilla,  tobacco,  quinine,  and  many  other  plant  substances, 
not  of  vital  importance,  are  much  used  by  men.  The  list  of 
valuable  plants  is  a  very  long  one. 

For  food  and  clothing,  plants  are  carefully  cultivated ;  but  for 
shelter  it  has  been  customary  to  depend  upon  the  forest,  which 
grows  without  care.  In  parts  of  Europe,  however,  so  much  of 
the  forest  has  been  removed  that  it  has  become  necessary  to  culti- 
vate even  the  forests,  planting  the  trees,  weeding  out  the  poor 
ones,  and  carrying  on  lumbering  with  great  care.  The  time  has 
now  arrived  in  America,  when  the  forest  needs  to  be  cultivated. 
Accordingly,  both  the  national  and  state  governments  have  set 
aside  large  tracts  as  forest  reservations.  A  division  of  the 
national  government  is  known  as  the  Bureau  of  Forestry,  and  a 


850  NEW  PHYSICAL   GEOGRAPHY. 

number  of  states  have  forestry  bureaus.  There  are  also  schools  of 
forestry,  like  those  at  Cornell,  Yale,  Wisconsin,  and  Michigan 
universities,  where  men  are  scientifically  trained  to  be  foresters. 

Summary. — Man  and  all  animals  rely  for  their  food,  either 
directly  or  indirectly,  on  the  vegetable  kingdom.  In  regions  imth 
a  cold  or  dry  season,  it  is  iiecessary  to  provide  food  for  the  unfavor- 
able season,  and  this  has  led  to  the  cultivation  and  improvement  of  a 
number  of  plants  for  their  seeds,  fruits,  bulbs,  and  tubers.  Many 
plants  are  also  used  to  supply  materials  for  clothing  and  shelter  ; 
and  now  even  forests  are  cared  for  by  methods  of  scientific  forestry. 

Topical  Outline    Review  Questions,  and  Suggestions. 

Topical  Outline.  —  209.  Importance  of  Air.  —  Carbon  dioxide; 
carbon  in  plant  tissues ;  extent  of  air ;  places  where  plants  are  absent. 

210.  Importance  of  Temperature. — ^ Effect  of  freezing;  temporary 
freezing;    effect  of  boiling;    plants  on  Greenland  ice;    in  hot  springs. 

211.  Importance  of  Sunlight.  —  Its  use;  plant  life  in  dark  places. 

212.  Importance  of  Water.  —  Use  of  water ;  sap ;  source  of  water. 

213.  Importance  of  Soil. — Water  plants;  epiphytes;  dependence  of 
most  land  plants  on  soil ;  plant  food  ;  effect  of  differences  in  soil. 

214.  Importance  of  Gravity.  —  Roots ;  stems  ;  wood ;  water  plants. 

215.  Influence  of  Climate.  —  Lowly  plants  ;  higher  plants ;  illustrations ; 
effect  of  temperature  ;  of  moisture. 

216.  Arctic  Flora. —  Rapid  growth;  kinds  of  plants;  clinging  to 
ground  ;  winter  ;  summer. 

217.  Temperate  Flora.  —  Timber  line  near  Arctic ;  evergreen  trees  ; 
kinds;  deciduous  trees;  kinds;  dormant  condition  in  winter;  perennial 
plants;  annuals;  treeless  regions;  sandy  soils;  "big  trees." 

218.  Tropical  Flora.  —  Subtropical  flora ;  tropical  trees ;  the  forest. 

219.  Flora  of  Savannas  and  Steppes.  —  Drought ;  plant  growth. 

220.  Desert  Flora.  —  Scattered  growth;  large  roots  ;  nature  of  leaves; 
cacti ;  plants  with  disagreeable  taste ;  proof  that  water  alone  is  lacking. 

221.  Mountain  Flora.  —  Tropical  zone;  temperate  zone;  timber  line; 
Alpine  flora  ;  flora  of  desert  highlands. 

222.  Water  Plants.  —  Position  ;  kinds  ;  adaptation  of  trees. 

223.  Means  of  Distribution.  —  Abundance  of  seeds  ;  devices  for  their 
spread;  distribution  —  wind,  animals,  rivers,  ocean  currents,  man. 

224.  Barriers  to  the  Spread  of  Plants.  —  The  ocean  barrier;  ocean- 
island  flora;  desert  barrier ;  mountain  barrier ;  wind  barrier, 


DISTRIBUTION  OF  PLANTS,  351 

225.  Variation  in  Plants.  —  Cause  of  struggle ;  illustration;  struggle 
for  existence ;  survival  of  the  fittest ;  evolution  ;  illustrations  of  causes  for 
evolution  ;  evolution  in  past ;  securing  protection  from  animals ;  making 
use  of  animals ;  effect  of  man  on  evolution. 

226.  Plants  of  Value  to  Man.  —  Dependence  on  plants;  plant  food  in 
warm  climates ;  in  places  with  an  unfavorable  season ;  parts  of  plants 
used ;  improvement ;  important  food  plants ;  source  of  food  plants ;  Ameri- 
can food  plants ;  plants  used  for  other  purposes ;  care  of  the  forest. 

Keview  Questions.  —  209.  What  do  plants  take  from  the  air? 
Where  are  plants  absent? 

210.  What  is  the  effect  of  cold?  Of  heat?  Give  an  illustration  of 
adaptation  of  plants  to  cold.     To  heat. 

211.  Of  what  importance  is  sunlight?     What  effect  has  darkness? 

212.  Of  what  importance  is  water?     How  is  it  obtained  ? 

213.  What  plants  are  not  dependent  on  soil  ?  Of  what  importance  is 
soil  to  land  plants?     Why  is  fertilizer  used? 

214.  State  the  effects  of  gravity  on  land  plants.     On  water  plants. 

215.  How  are  plants  influenced  by  climate  ?     Give  illustrations. 

216.  State  the  peculiarities  of  plant  life  in  the  Arctic. 

217.  What  are  the  conditions  of  tree  growth  near  the  frigid  zone? 
In  the  warmer  temperate  zone?  In  what  ways  are  plants  adapted  to 
winter  conditions?  How  does  the  flora  of  the  temperate  zone  vary? 
What  conditions  favor  the  "  big  trees"? 

218.  What  is  the  subtropical  flora?  Name  some  of  the  tropical  trees. 
What  are  the  characteristics  of  the  tropical  forest? 

219.  What  are  the  characteristics  of  the  flora  of  savannas  and  steppes? 

220.  How  are  desert  plants  fitted  to  survive  periods  of  drought?  How 
are  they  protected  from  animals  ?     What  do  the  oases  prove  ? 

221.  What  changes  occur  in  the  flora  of  mountains?  Compare  Alpine 
and  Arctic  flora.     What  are  the  conditions  on  highlands  in  deserts? 

222.  What  kinds  of  plants  thrive  in  water?  How  are  trees  adapted 
to  water  life  ? 

223.  Why  are  so  many  seeds  produced  ?  What  devices  are  there  '.o 
aid  in  the  spread  of  seeds?     By  what  agencies  are  plants  spread? 

224.  Why  is  water  a  barrier  ?  How  is  it  certain  that  the  ocean  is  not 
an  absolute  barrier?     What  other  barriers  are  there? 

225.  For  what  are  plants  struggling  ?  Give  an  illustration.  What  is 
the  result  of  the  struggle?  What  do  fossils  prove?  Give  two  illustra- 
tions of  how  changes  on  the  earth  may  influence  evolution.  What  is  the 
effect  of  the  relation  between  plants  and  animals?  How  is  man  infla- 
encing  evolution  ? 

226.  How  is  man  dependent  on  plants  ?      What  is  the  condition  in 


352  NEW  PHYSICAL   GEOGRAPHY. 

warm  climates?  In  regions  with  cold  or  dry  seasons?  What  parts  of 
plants  are  used  for  food?  What  effect  has  cultivation  had?  Where 
have  the  cultivated  plants  come  from  ?  For  what  other  purposes  are 
plants  used  ?     What  is  now  being  done  with  the  forest  ? 

Suggestions.  —  (1)  Place  a  hardy  plant,  such  as  moss,  in  boiling 
water  for  a  few  minutes,  and  plant  it  to  see  if  it  will  grow  again. 
(2)  Freeze  the  same  plant  for  a  night  and  see  if  it  will  grow.  Freeze 
a  delicate  plant,  for  example  a  geranium,  and  see  if  it  will  continue  to 
grow.  (8)  Place  a  plant,  say  a  geranium,  in  the  cellar  and  let  it  grow 
for  a  few  weeks,  and  note  the  change.  (4)  Leave  a  plant  in  its  pot  with- 
out water  and  see  if  it  grows.  Keep  water  up  to  the  top  of  the  earth  (a 
swamp)  and  see  if  it  kills  the  plant.  Get  a  cactus  and  see  if  it  will  live 
in  dry  soil.  Study  the  cactus.  (5)  Using  the  same  kind  of  seed,  try 
growing  plants  in  several  different  kinds  of  soil,  —  sandy,  fertile  loam,  etc., 
and  see  which  thrives  best.  (6)  Try  to  burn  ash.  Perhaps  the  teacher 
of  chemistry  can  suggest  an  experiment  to  prove  that  there  is  mineral 
matter  in  ash.  (7)  Put  a  plant  in  a  pot,  inclining  it  at  an  angle  to  the 
surface.  Will  it  keep  on  growing  in  that  direction?  (8)  Collect  and 
study  seeds  to  see  what  devices  they  use  for  distribution.  (9)  Plant  a  bean 
in  a  flower  pot  in  absolutely  dry  earth  (a  desert).  Does  it  sprout?  Place 
one  in  a  jar  of  water.  Does  it  grow  after  it  has  used  up  the  nourishment 
in  the  seed?  This  illustrates  why  deserts  and  water  are  barriers. 
(10)  Study  the  flora  of  your  vicinity  to  see  if  the  plants  vary  in  kind 
from  one  soil,  or  exposure,  to  another.  If  there  is  a  swamp,  find  how 
the  swamp  plants  are  different  from  those  on  dry  slopes.  (11)  What  crops 
are  raised  in  your  vicinity?  What  crops  cannot  be  raised?  Why?  Is 
there  a  difference  in  crops  according  to  the  soil?  (12)  Make  a  list  of 
plants  valuable  to  man,  their  principal  uses,  and  the  localities  from  which 
they  come.  Let  each  student  make  a  list,  then  combine  it  for  the  use  of 
the  whole  class. 

Reference  Books.  —  Coulter,  Plant  Relations,  Appleton  &  Co.,  New 
York,  1899,  $1.10  ;  Merriam,  Life  Zones  and  Crop  Zones  of  United  States, 
Department  of  Agriculture,  Biological  Survey  Division,  Bull.  10,  1898, 
Washington,  D.C. ;  Bailey,  Plant  Breeding,  Macmillan  Co.,  New  York, 
1895,  $1.00;  Survival  of  the  Unlike,  Macmillan  Co.,  New  York,  1896,  $2.00; 
Fernow,  Economics  of  Forestry,  Crowell  &  Co.,  New  York,  1902,  $1.50; 
GiFFORD,  Practical  Forestry,  Appleton  &  Co.,  New  York,  1902,  $1.20. 


Fig.  501.  —  Cutting  sugar  cane  in  Louisiana. 


Fig.  502.  —  Picking  tea  in  India. 


Fig.  503.  —  Picking  cotton  in  southern  United  States, 


Fia.  604.  —  A  pineapple  field  in  the  Hawaiian  Islands. 


CHAPTER   XVIII. 

DISTRIBUTION    OF   ANIMALS. 

227.  Influence  of  Surroundings.  —  Plants  and  animals  are 
alike  in  being  dependent  for  life  on  their  surroundings. 
Like  plants,  all  animals,  even  those  on  the  sea  bottom,  need 
air  to  breathe  ;  all  require  water  for  their  blood  and  tissues : 
and  for  all  it  is  necessary  that  the  temperature  shall  be  neither 
too  high  nor  too  low.  Temperatures  near  the  boiling  point, 
or  long  continued  below  the  freezing  point,  are  fatal  to  animal 
tissues.  Many,  especially  the  lower  animals,  are  able  to  sur- 
vive a  period  of  freezing  ;  others  protect  themselves  by  a  coat 
of  fur,  feathers,  or  fat ;  and  some,  such  as  bears,  lie  dormant 
in  a  protected  place  during  the  cold  season. 

Most  water  and  many  land  animals  are  cold-blooded;  that  is, 
Mieir  temperature  changes  with  their  surroundings.  They  re- 
quire so  little  air  that  many  of  them  obtain  ail  they  need  from  the 
water.  Other  animals,  the  birds  and  mammals,  are  warm-blooded, 
the  warmth  being  due  to  slow  combustion  caused  within  their 
bodies  by  the  oxygen  they  breathe  (p.  229).  Such  animals  require 
much  oxj^gen  and,  even  if  they  live  in  water,  as  the  whales  do, 
must  rise  to  the  air  to  obtain  it.  Those  that  live  in  water,  or  in 
cold  climates,  need  to  protect  themselves  by  a  warm  covering  in 
order  to  keep  the  warmth  in  their  blood. 

Animals  differ  from  plants  in  the  way  in  which  they  secure 
food.  While  some  remain  fixed  in  one  place,  depending  on 
supplies  brought  to  them,  as  plants  do,  most  animals  seek  their 
food.  They  need  carbon  and  mineral  substances,  but  are  unable 
to  secure  them  directly  from  air  and  earth.  They  depend  upon 
plants  to  perform  this  work,  and  the  basis  of  animal  food  is,  there- 
fore, plant  life.  Even  the  food  of  flesh-eating  animals  may  ])Q 
2  A  353 


354  NEW  PHYSICAL   GEOGUAPHY. 

traced  back  to  the  plant  kingdom.     Thus  plants  are  of  vital  impo^ 
tanco  to  animals. 

Unlike  plants,  animals  do  not  absolutely  require  sunlight,  since 
they  do  not  need  it  to  transform  air,  water,  and  mineral  matter  to 
food,  as  plants  do.  Consequently,  animals  are  able  to  live  even 
in  the  darkness  of  the  deep  sea. 

Like  plants,  animals  are  strikingly  adapted  to  their  sur- 
roundings ;  if  they  were  not,  they  would  perish.  Some  spend 
most  of  their  time  in  the  air  ;  some  live  part  or  all  of  the 
time  in  water  ;  some  dwell  in  trees  ;  some  have  homes  on 
the  land  surface  ;  and  some  dwell  at  least  part  of  the  time 
underground.  Flying,  climbing,  swimming,  and  running 
are  developed  to  aid  either  in  securing  food  or  in  escaping 
enemies.  For  these  purposes  there  are  many  modifications 
in  the  shape  of  the  body,  —  for  example,  wings  for  flying ; 
long  arms,  claws,  and  tails  for  climbing  ;  fins  and  boat- 
shaped  bodies  for  swimming  ;   long  legs  for  running. 

Gravity  influences  the  form  and  structure  of  the  body.  Since 
man  stands  upright,  two  legs  only  are  required  ;  but  four  legs  are 
necessary  to  sustain  a  body  that  extends  parallel  to  the  ground. 
Strong  bones,  or  other  structures,  are  needed  to  support  the  body 
on  land ;  but  in  water,  which  is  denser,  bones,  where  present,  are 
much  lighter.  To  maintain  themselves  in  the  air,  flying  birds 
have  more  feathers  and  lighter  bones  than  running  birds,  and 
in  most  cases  their  bodies  are  smaller. 

Summary.  —  All  animals  must  have  air  for  breathing,  water  for 
blood  and  tissues,  and  a  temperature  neither  too  high  nor  too  low. 
There  are  both  ivann  and  cold  blooded  animals,  and  all  are  depend- 
ent on  the  plant  kingdom  for  food.  Animals  are,  in  many  ivays, 
adapted  to  their  surroundings  ;  and  there  are  many  modifications 
fitting  them  to  secure  food  and  escape  enemies.  Gravity  influences 
the  form  and  structtwe  of  the  body  in  many  ways. 

228.    Animal  Life,  or  Fauna,^  of  the  Arctic. — No  animals 

^  A  fauna  is  tlie  aaaenib]a;5e  of  animals  occupying  a  region.  Thus  we 
may  spealc  of  a  Greei\laud  fauna,  an  Alaskan  fauna,  etc. 


■^     ''\j^ 

^-^' 


<;#- 


ARCTIC  rox 


PTARMIGAN 


,s^ 


GREAT AUK 

f-JO-.V    EXTINCT 


CARIBOU 


MUSK  OX 


Fig.  505.  —  A  group  of  Arctic  animals. 


Fig.  50t).  —  Polar  bear  and  Arctic  seal.  The 
legs  of  the  seal  are  changed  to  finlike 
appendages,  used  for  swimming  and  for 
climbing  upon  the  ice. 


Fig.  507.  —  \Valrus.  Tlie  legs 
have  been  modified  for 
swimming  and  for  climbing 
upon  the  ice. 


Fig.  508.  —  Arctic  whale.  The  legs  have  almost  disappeared,  and  the  tail  is  usi-u 
for  swimming.  In  the  mouth  of  this  whale  is  a  large  amount  of  valuable 
'vbalebone,  on  the  edges  of  which  are  fringes  which  strain  from  the  wat^\ 
'iie  small  animalcule,  upon  which  the  whale  lives. 


DISTRIBUTION   OF  ANIMALS.  355 

live  in  the  ice-covered  interior  of  (xreenland  ;  but  in  and  near 
the  Arctic  Ocean  there  is  much  life,  especially  in  summer. 
There  are  many  kinds  of  fishes  and  other  sea  animals,  and 
a  great  variety  of  sea  birds  feeding  on  them.  When  the 
freezing  of  the  sea  and  land  cuts  off  their  food  supply,  most  of 
the  birds  are  forced  to  go  southward  ;  wild  geese,  for  instance. 
wJiich  spend  the  summer  on  the  tundras  of  northern  Amer- 
ica, fly  as  far  south  as  Mexico.  Other  species  go  no  farther 
south  than  Labrador  and  Newfoundland.  During  the  sum- 
mer, birds  congregate  in  great  numbers  in  their  breeding 
places  and,  when  frightened  from  their  nests  on  the  cliffs,  rise 
into  the  air  in  clouds. 

On  the  land  there  are  crows,  ptarmigans,  and  some  smaller 
birds;  also  hares,  foxes,  reindeer  (called  caribou  in  America), 
and  musk  ox  (Fig.  505).  There  are  practically  no  reptiles, 
for  the  great  cold  is  unfavorable  to  such  cold-blooded  animals; 
but  there  are  numerous  insects,  of  which  the  mosquito  is 
especially  abundant. 

A  number  of  mammals  live  part  or  all  of  the  time  in  the 
sea.  The  polar  bear  spends  most  of  his  time  on  the  sea  ice, 
seeking  the  seal  for  food  (Fig.  506).  There  are  walruses 
(Fig.  507)  and  a  number  of  species  of  seal,  —  warm-blooded, 
air-breathing  mammals,  which  now  and  then  leave  the  sea 
for  a  short  time  and  take  to  the  ice  or  shore.  Whales  also 
live  in  the  Arctic  (Fig.  508),  but,  though  air-breathing,  they 
never  leave  the  water. 

The  warm-blooded  animals  are  well  adapted  to  life  in  the  severe 
Arctic  climate.  They  are  well  protected,  the  birds  with  warm 
feathers  and  down,  which  keep  out  wind,  water,  and  cold,  the 
mammals  with  fur  or  fat,  or  both.  In  winter,  when  most  needed, 
the  fur  is  thickest.  Eider  down  and  the  fur  of  the  fur  seal  of 
Bering  Sea  are  highly  valued  for  their  warmth  and  beauty. 

Many  Arctic  animals,  like  the  fox,  hare,  and  polar  bear,  are 
white  like  the  snow  and  ice  around  them,  thus  escaping  notice, 
both  from  their  foes  and  their  prey.     The  ptarmigan  becomes  white 


356  NEW  PHYSICAL   GEOGRAPHY. 

ill  winter;  but  its  summer  plumage  resembles  the  vegetation  amid 
which  it  feeds.     The  baby  seal,  which  spends  its  first  days  on  the 
,  ice,  is  also  white;  but  as  it  grows  older,  and  takes  to  the  water,  its 
color  changes  to  more  nearly  resemble  the  water. 

Summary.  —  In  the  Arctic  region  there  are  many  sea  birds,  which 
move  southward  in  winter  ivhen  the  freezing  of  sea  and  land  cuts  off 
their  food  supjt/y.  On  the  land  there  are  a  few  birds  and  mammals, 
numerous  insects,  but  practically  710  reptiles.  A  number  of  mammals 
live  part  or  all  of  the  time  in  the  sea.  Warm-blooded  Arctic  animals 
are  protected  from  the  cold  by  far,  feathers,  and  fat,  and  are  often 
white  like  the  surrounding  snow  and  ice. 

229.  Temperate  Fauna.  —  In  the  temperate  zones  animal 
life  is  more  varied,  and  differs  greatly  from  place  to  place. 
Certain  species,  like  the  bison  (Fig.  518)  and  antelope,  have 
become  especially  adapted  to  life  on  open  plains;  others,  like 
the  moose  and  squirrel,  to  the  forest;  others,  like  the  moun- 
tain sheep  and  chamois,  to  high  mountains;  others,  like  the 
jack  rabbit,  coyote,  and  camel,  to  arid  lands.  Some,  like 
the  blindfish,  live  in  caves,  losing  their  eyes  because  they 
are  not  needed  in  the  darkness.  Still  others,  like  the  earth- 
worm, Avoodchuck,  prairie  dog,  and  mole,  burrow  in  the  soil, 
spending  part  or  all  of  their  lives  underground.  Some,  like 
the  owl  and  wild  cat,  sleep  by  day  and  hunt  by  night ;  but 
the  majority  rest  when  it  is  dark. 

An  enumeration  of  all  the  animals  of  the  temperate  zones  would 
be  along  list,  for  there  is  much  variety  among  mammals,  birds, 
reptiles,  insects,  and  other  groups.  Among  the  birds  are  hawks, 
eagles,  owls,  hunmiing  birds,  thrushes,  and  a  large  number  of 
singing  birds;  and  along  the  coast  there  are  many  sea  birds,  in- 
cluding gulls,  terns,  ducks,  and  snipe.  Among  mammals  are  the 
bear,  fox,  wolf,  deer,  antelope,  elk,  moose,  wild  cat,  squirrel,  and 
hare,  besides  others  mentioned  above  (Figs.  509,  510).  One 
peculiar  animal  of  the  United  States  is  the  opossum,  which  be- 
longs to  the  same  division  of  the  animal  kingdom  as  the  kangaroo. 

!Many  animals  of  the  temperate  zone  are  protected  by  a  coat  of 


Fig.  509.  —  A  group  of  cold  temperate  ^Qiericaa  auiniais. 


B  «.  filO.  —  A  group  of  animals  of  western  United  States,  founa  in  Uie  mountains 

or  on  the  arid  plains  and  plateaus. 


DISTRIBUTION  OF  ANIMALS.  357 

• 

fur,  highly  prized  by  man.  Fur-bearing  animals  of  value,  including 
mink,  otter,  sable,  and  beaver,  are  found  especially  in  the  cold 
north,  where  they  are  still  hunted.  The  beaver  (Fig.  509),  a  very 
interesting  animal,  cuts  down  trees  and  bushes  with  which  to  build 
dams  to  make  ponds  and  swamps  in  which  its  plant  food  grows. 
His  sharp  teeth  and  flat  tail  are  especially  adapted  to  this  work. 

Summary.  —  Animal  life  in  the  temperate  zone  is  abundant  and 
varied,  different  species  being  adapted  to  life  on  the  prairies,  in  the 
forest,  on  mountains,  in  arid  lands,  in  caves,  and  underground. 
Many  mammals  have  far  of  value  to  man. 

230.  Tropical  Fauna.  —  Since  plants  are  the  basis  for  ani- 
mal food,  animal  life  thrives  where  plants  abound.  Hence, 
animals  are  abundant  in  the  tropical  forest.  Innumerable 
insects,  fe.eding  on  pollen,  honey,  leaves,  bark,  wood,  or  decay- 
ing vegetation,  some  in  trees  and  some  on  the  ground,  furnish 
food  for  countless  birds.  The  insects  include  many  beauti- 
ful butterflies ;  also  the  interesting  white  ants,  or  termites, 
which  build  great  structures  of  earth  in   which  to  dwell. 

The  birds,  including  parrots,  paroquets,  humming  birds, 
and  birds  of  paradise,  number  thousands  of  species.  There 
are  also  many  reptiles,  including  turtles,  alligators,  lizards, 
and  snakes.  Among  the  snakes  are  venomous  species,  and 
huge  boa  constrictors,  Avhich,  hanging  from  the  trees,  resem- 
ble thick  vines.  One  of  the  lizards,  the  iguana,  attains  a 
length  of  several  feet.  The  mammals  include  the  lion,  tiger, 
hippopotamus,  rhinoceros,  giraffe,  and  elephant  of  the  Old 
World  (Figs.  511,  512),  and  the  jaguar,  puma,  tapir,  arma- 
dillo, and  sloth  of  the  New  (Fig.  514).  There  are  also 
monkeys,  orang-outangs,  gorillas,  antelope,  deer,  zebras,  and 
many  other  mammals. 

Summary.  —  The  abundance  of  plants  in  the  tropical  zone  permits 
the  existence  of  a  great  variety  of  insects,  birds,  reptiles,  arid  mammals. 

231.  Desert  Fauna.  —  A  complete  list  of  the  desert  ani- 
mals would  be  much  shorter  than  that  of  a  humid  forest 


358  NEW  PHYSICAL   GEOGRAPHY, 

region.  There  is  a  great  contrast  between  the  abundance 
and  variety  of  life  in  the  African  forest  and  its  paucity  in 
the  Sahara  desert.  There  is  also  a  decided  contrast  between 
the  abundant  and  varied  life  in  an  Arkansas  forest  and  the 
limited  fauna  of  the  desert  portion  of  southwestern  United 
States.  There  the  chief  animals  are  the  antelope,  puma, 
coyote,  jack  rabbit,  cotton-tail  rabbit,  rattlesnake  (Fig.  510), 
horned  toad,  and  a  limited  number  of  birds  and  insects. 

Animals  need  to  be  peculiarly  adapted  for  life  on  a  desert ;  and 
their  number  and  variety  are  limited  by  the  small  amount  of  water 
and  plant  food.  Some,  like  the  snakes,  require  little  water,  aside 
from  what  they  secure  from  the  animals  they  eat ;  others  are  sup- 
plied with  water  from  the  roots  or  stems  of  the  desert  plants 
upon  which  they  feed ;  and  still  others  live  near  springs,  or  go 
long  distances  to  them.  The  camel  (Fig.  512)  is  wonderfully 
adapted  to  desert  life.  It  is  able  to  make  long  journeys  on  the 
desert  because  of  the  store  of  water  which  it  carries  in  its  water 
pouch ;  its  broad,  flat  feet  are  admirably  suited  for  travel  over 
sandy  surfaces ;  and  its  nostrils  may  be  closed  to  keep  out  sand 
which  the  wind  blows  about. 

Summary.  —  77ie  dryness  of  the  climate,  and  the  scarcity  of  plant 
food,  limit  animal  life  in  the  desert  ;  hut  some  species,  like  the  camel, 
are  peculiarly  adapted  to  such  a  life. 

232.  Fresh-water  Fauna.  —  Rivers  and  lakes  have  varied 
faunas,  including  especially  fishes,  insects,  and  lower  inver- 
tebrates, or  animals  without  a  backbone.  Among  fishes  many 
are  of  value  for  food,  and  some,  such  as  salmon  and  shad, 
come  from  the  sea  into  fresh  water  to  lay  their  eggs.  A  num- 
ber of  birds  and  mammals,  such  as  the  duck,  beaver,  muskrat, 
mink,  hippopotamus,  and  manatee  or  sea  cow  (Fig.  514),  spend 
part  or  all  of  their  time  in  fresh  water,  feeding  on  water 
plants  and  animals.  Many  insects  and  amphibia  (toads, 
frogs,  salamanders,  etc.)  breed  in  water,  coming  to  dry  land 
during  a  later  stage.  Numerous  reptiles,  including  croco- 
diles, alligators,  turtles,  and  some  snakes,  live  in  fresh  water. 


ELEPHANT 


Fig.  511.  — a  group  of  African  tropical  animals. 


Fig.  512  —  A  group  of  southern  Asiatic  animals 


DISTRIBUTION   OF  ANIMALS.  359 

There  are  many  differences  in  fresh-water  life.  For  example, 
the  faunas  of  muddy  water,  sandy  bottoms,  swampy  ponds, 
quiet  water,  and  flowing  rivers  are  quite  different.  Cold 
water  supports  less  abundant  and  varied  faunas  than  warm ;  and 
salt  lakes  have  very  few  animals.  The  Dead  Sea  receives  its  name 
because  of  the  general  absence  of  life,  contrasting  strikingly  with 
the  fauna  of  the  neighboring  fresh-water  Sea  of  Galilee. 

When  arms  of  the  sea  are  inclosed  and  changed  to  fresh  water, 
most  of  the  marine  animals  die,  though  some  species  may  survive  •, 
also  marine  animals  that  enter  fresh  water  may  be  prevented  from 
returning  to  the  sea.  The  landlocked  salmon  is  a  sea  fish  that 
has  adapted  itself  to  permanent  life  in  fresh  Avater. 

Summary.  —  Lower  invertebrates,  insects,  fish,  bii'ds,  mammals, 
amphibia,  and  reptiles  are  adajjted  to  life  in  fresh  water;  and  faunas 
vary  with  surrounding  conditions. 

233.  Homes  of  Animals. — As  a  whole,  invertebrate  animals  are 
peculiarly  suited  to  life  in  water.  Insects  are  the  principal  excep- 
tion, though  spiders,  snails,  and  other  invertebrates  are  also  land 
dwellers.  While  most  insects  live  on  land,  many  live  in  fresh 
water,  and  a  few  in  the  sea ;  and  some,  such  as  the  mosquito, 
spend  the  early  part  of  their  life  in  the  water. 

Reptiles  and  amphibia  are  inhabitants  of  both  land  and  fresh 
water,  though  some,  like  the  turtle,  live  in  the  sea. 

While  some  birds,  such  as  the  penguin,  ostrich,  emu,  and  rhea, 
are  unable  to  fly,  most  birds  are  especially  fitted  to  live  partly  in 
the  air  and  partly  in  trees  or  on  the  ground.  Many,  like  the 
duck  and  penguin,  spend  much  of  their  time  in  the  water. 

Mammals  are  mainly  land  dwellers ;  but  the  limbs  of  the  bat 
have  been  changed  for  use  in  flight,  and  of  the  seal,  walrus,  sea 
cow,  and  others  for  use  in  swimming.  Not  a  few,  like  the 
monkey,  sloth,  opossum,  wild  cat,  and  jaguar,  spend  most  of  their 
lives  in  trees. 

Summary. —  Invertebrates  are  typically  water  dioellers,  though 
some  groups,  especially  most  of  the  insects,  live  on  the  land.  Rep- 
tiles and  amphibia  are  land  and  water  dwellers;  birds,  typical  air 
dwellers,  are  also  found  in  the  water  and  on  the  ground;  mammals^ 
typical  land  divellers,  are  also  found  in  the  air  and  water. 


360  NEW  PHYSICAL   GEOGBAPHY. 

234.  spread  of  Animals.  —  As  in  the  case  of  plants,  there 
is  a  tendency  for  animals  to  spread.  To  insure  this,  more 
young  are  born  than  can  possibly  live,  some  dying  for  lack  of 
food,  others  being  killed  by  enemies.  It  is  during  the  young 
stage  that  animals  are  least  able  to  protect  themselves,  and 
those  animals,  like  fishes,  which  do  not  protect  their  young, 
must  lay  thousands  of  eggs  in  order  that  one  of  their  off- 
spring may  reach  maturity. 

It  is  a  great  step  in  advance  when  the  young  are  pro- 
tected and  fed  by  the  parents,  as  among  birds  and  mammals, 
or  among  bees  and  some  other  insects.  Then,  since  they 
receive  protection  during  the  critical  stage  of  youth,  fewer 
offspring  are  necessary.  Those  animals  that  take  the  best 
care  of  their  offspring  are  the  highest. 

The  tendency  to  spread  has  taken  animals  to  all  parts 
of  the  earth;  and  evolution,  or  the  tendency  to  change  so  as 
to  become  better  adapted  to  surroundings,  has  caused  them  to 
vary.  It  is  because  of  evolution  that  tlie  European  reindeer 
and  American  caribou,  though  of  the  same  stock,  are 
slightly  different.  The  African  elephant  is  a  different  spe- 
cies from  that  of  Asia,  though  from  the  same  original  source; 
and  the  mammoth  and  mastodon,  living  in  a  cold  climate,  had 
a  hairy  coat,  quite  unlike  the  elephants  of  warm  regions. 

Ocean  dvyellers  (p.  195)  are  among  the  most  widespread 
of  anintarl|.;  They  swim,  or  are  drifted,  here  and  there; 
and  their  surroundings  are  so  uniform  that  there  is  little 
reason  for  change.  Because  they  can  fly,  insects,  birds, 
and  bats  are  among  tlie  most  Avidely  distributed  of  land  ani- 
mals. Those  animals  tliat  walk  or  crawl  move  more  slowly, 
meet  more  enemies,  and  find  more  barriers  to  overcome,  such 
as  rivers,  mountains,  deserts,  and  sea.  For  these  reasons  tlie 
large  mammals  and  running  birds  are  usually  confined  to 
limited  areas.  Yet  some,  especially  the  fierce  carnivorous 
animals,  cover  a  wide  range;  the  tiger,  for  example,  lives  in 
the  hot  jungle,  on  open  plains,  and  on  cool  movmtaiii  slopes. 


DISTRIBUTION  OF  ANIMALS.  361 

Summary.  — Many  anwials  make  provision  for  the  spread  of  thn 
species  by  the  j^rodnctiou  of  numerous  offspring  ;  but  higher  animals 
protect  their  young  so  that  feiver  offspring  are  necessary.  Animals 
have  migrated  to  all  parts  of  the  earth,  fitting  themselves  by  evolution 
to  their  surroundings.  Ocean  and  fiying  animcds  are  most  tvidely 
distributed,  ichile  land  dwellers  move  more  slowly  and  are  often  coiv 
fined  to  very  limited  areas. 

235.  Barriers  to  the  Spread  of  Animals.  —  The  spread  of 
animals  is  interfered  with  by  the  same  barriers  as  in  the  case 
of  plants.  Water  is  the  greatest  barrier,  but  it  is  overcome 
by  flying  animals  and  by  those  small  forms  that  may  be 
drifted,  clinging  to  logs.  The  tropical  forest  is  a  barrier  to 
a  desert  animal,  and  the  desert  to  one  that  needs  water 
every  day.  Nor  can  animals  accustomed  to  a  warm  climate 
or  to  life  on  plains,  easily  cross  to  the  other  side  of  a  cold, 
rugged  mountain  range.  Thus  very  different  faunas  may 
exist  on  opposite  sides  of  such  barriers,  though  some  species, 
especially  those  that  fly,  will  be  the  same  on  both  sides. 

Summary.  —  T7ie  same  barriers  —  ivater,  desert,  and  mountain — 
affect  both  animcds  and  i:)lants ;  they  are  most  easily  overcome  by 
flying  animcds. 

236.  Island  Faunas.  —  The  influence  of  the  ocean  as  a 
barrier  is  well  illustrated  by  the  Bermuda  Islands,  which  lie 
about  600  miles  east  of  the  Carolina  coast,  the.  nearest  land; 
They  have  never  been  connected  with  the  continent,  and  yet 
the  animals  and  plants  are  quite  like  those  of  the  mainland. 
The  flora  includes  the  cedar  and  other  northern  plants,  and 
cactus,  palmetto,  oleander,  and  other  southern  forms. 

The  fauna  consists  principally  of  insects  and  birds,  in- 
cluding ground  doves,  redbirds,  bluebirds,  and  catbirds,  like 
those  on  the  mainland.  A  small  West  Indian  lizard  is  also 
found ;  and  there  are  bats,  the  only  native  mammals. 

The  lizards,  and  some  of  the  insects,  were  probably  drifted 
there  by  ocean  currents  ;  the  birds,  bats,  and  many  insects* 


362  NEW  PHYSICAL   GEOGRAPHY, 

flew  across  ov  were  drifted  by  the  wind.  Every  year  birds 
from  the  mainland  are  seen  in  Bermuda,  some  resting  during 
migration,  others  driven  out  to  sea  by  winds. 

It  is  not  at  all  uncommon,  far  from  land,  to  see  small  birds 
resting  on  the  spars  and  decks  of  vessels;  and  even  the  tiny 
humming  bird  has  found  its  way  as  far  as  Bermuda.  Doubt- 
less the  small  land  birds,  driven  out  to  sea  during  storms,  find 
resting  places  on  logs  and  clusters  of  floating  seaweed  ;  but  many 
must  perish. 

Similar  conditions  exist  in  the  A  zores,  off  the  European  coast, 
and  the  Galapagos  Islands,  west  of  South  America.  The  word 
Azores  means  hawk,  and  Galapagos,  turtle,  the  names  being  given 
because  these  animals  were  common  when  the  islands  were  dis- 
covered. Animals  have  crossed  the  ocean  barrier  to  even  the 
most  remote  islands,  like  the  Hawaiian  Islands  in  the  mid-Pacifio. 

Summary.  —  The  Bermuda^  and  other  islands,  even  the  most 
remote,  have  plant  and  animal  life  from  the  mainland,  shoicing  that 
the  ocean  barrier  can  he  crossed.  Every  year,  birds  stop  on  the  Ber- 
mudas during  migration,  or  because  drifted  oat  to  sea  by  storms. 

237.  Australian  Fauna.  — The  fauna  and  flora  of  Australia 
are  both  peculiar.  Among  the  birds  are  the  emu  and  casso- 
wary, two  running  birds  ;  also  parrots,  lyre  birds,  and  other 
peculiar  kinds.  The  mammals  include  several  species  of  mar- 
supials, the  very  peculiar  monotremes^  and  a  few  other  species 
(Fig.  513).  The  monotremes,  the  lowest  order  of  mammals, 
are  represented  by  the  remarkable  duck-billed  platypus  (Fig. 
513),  which,  unlike  other  mammals,  lays  eggs.  The  marsu- 
pials, another  low  order  of  mammals,  to  which  the  opossum 
belongs,  include  the  kangaroo.  These  animals  carry  their 
young  in  a  pouch,  and,  instead  of  walking,  liop  about  by 
means  of  their  long  hind  legs  and  stout  tail.  Alth(mgh 
higher  forms  of  mammals  inhabit  southern  Asia  and  the  East 
Indies,  they  liave  not  found  their  way  to  Australia. 

The  explanation  of  this  peculiar  life  is  as  follows.  Fossils  in 
t>i.e  rocks  prove  that,  far  back  in  time,  monotremes  and  marsupials 


RABBIT 


KOALA 


^  ^ 
^'^ 


EMU 


li 


ECHIDNA 


1 


~:P 


\ 


'^ 


-"4- 


PLATYPUS 


^n 


KANGAROO 


Fig.  513  —  A  group  of  Australian  animals. 


p         „:^ 

m        SLOTH 

l/"^' 

U%  ] 

■TAPIR 

Fig.  514.  —  A  group  of  South  Anierican  animals. 


DISTRIBUTION  OF  ANIMALS,  363 

were  widespread.  Australia  was  then  so  connected  with  other 
continents  that  these  animals  were  able  to  migrate  there.  Fiercer 
animals  have  developed  in  the  other  continents  and  have  killed 
off  the  monotremes  and  most  of  the  marsupials ;  but  they  have 
been  prevented  from  reaching  Australia  because  sinking  of  the 
land  has  cut  off  its  connection  with  other  continents.  Therefore 
animals  that  belong  to  the  geological  yesterday  are  to-day  living 
in  Australia,  though  unfit  to  survive  in  other  lands.  They  remain 
there  only  because  the  ocean  protects  them  from  the  invasion  of 
stronger  species.  Even  dogs,  introduced  by  man,  and  now  run- 
ning wild,  are  playing  havoc  among  the  defenseless  marsupials. 

Summary.  —  The  Australian  fauna  is  peculiar,  because  the  ocean 
barrier  has  prevented  stronger  species,  developed  on  other  continents, 
from  entering  and  destroying  the  defenseless  animals  that  came  long 
ago,  before  these  stronger  species  had  been  evolved,  and  when  Aus- 
tralia was  united  loith  other  lands. 

238.  South  American  Fauna.  —  South  American  animals  are  also 
peculiar,  though  less  so  than  those  of  Australia.  The  huge  condor 
(Fig.  514),  the  largest  of  flying  birds,  lives  there;  also  the  rhea,  a 
running  bird,  sometimes  called  the  American  ostrich;  the  llama 
and  its  allies ;  various  species  of  monkey;  the  sloth;  the  ant-eater; 
the  armadillo;  the  tapir;  and  other  strange  forms  (Fig.  514).  The 
fact  that  these  peculiar  animals  exist  in  South  America,  while 
only  part  of  them  extend  up  into  southern  North  America,  leads 
to  the  belief  that  South  America  has  also  been  cut  off  from  other 
lands,  though  not  for  so  long  a  time,  nor  so  continuously,  as 
Australia. 

Summary.  —  TJie  peculiar  fauna  of  South  America  also  indicates  a 
former  separation  from  other  lands,  but  not  so  long  or  so  continuous 
as  in  the  case  of  Australia. 

239.  Faunas  of  Other  Continents.  —  There  is  much  closer  resem- 
blance between  the  life  on  other  continents.  In  the  north  tem- 
perate zone  there  is  such  resemblance  as  to  lead  to  the  belief  that 
there  has  been  even  better  connection  in  the  past  than  at  present. 
For  example,  hairy  elephants  (mammoths  and  mastodons),  now 
extinct,  lived  in  Siberia,  Europe,  and  North  America;  and  among 


364  NEW  PHYSICAL   GEOGRAPHY, 

living  animals,  there  are  close  resemblances  throughout  th^  (vhole 
region.  The  faunas  of  Africa  and  southern  Asia  are  als^  quite 
alike  (Figs.  511,  512),  indicating  close  connection. 

Summary. —  TJiere  is  close  resemblance  between  the  faimah  of 
northern  Asia,  Europe,  and  America;  also  Africa  and  southern 
Asia,  hidicating  former  land  connection. 

240.  Zones  of  Animal  Life. —  The  distribution  of  animals, 
♦lescribed  above,  has  led  to  the  division  of  the  earth  into 
several  zones,  realms  and  regions  (Fig.  515),  each  differing 
in  important  respects  from  the  others.  The  differences  be- 
tween these  zones  are  due  to  two  principal  facts:  (1)  that 
barriers  —  mountain,  desert,  and  ocean  —  have  cliecl^ed  the 
spread  of  animals ;  and  (2)  that  evolution  has  developed 
animals  of  different  kinds  on  opposite  sides  of  a  barrier.  The 
boundaries  of  these  zones  are  not  sharply  marked,  nor  are  the 
zones  absolutely  unlike ;  for  some  species  will  find  their  way 
across  even  the  greatest  barrier. 

Summary.  —  Barriers  and  evolution  have  caused  such  differences 
among  ayiimals  that  several  zones  of  animal  life  are  recogiiized. 

241.  Influence  of  Man.  —  Man  has  been  a  very  important 
agent  in  causing  changes  among  animals.  In  most  parts  of 
the  world  he  has  come  in  as  an  enemy,  either  seeking  animals 
for  his  food  or  killing  them  because  they  destroy  it.  As  a 
result,  he  has  caused  such  a  decrease  among  large  wild  ani- 
mals that,  in  parts  of  America  and  Europe,  very  few  remain. 

Some  species,  like  the  bison,  have  been  almost  exterminated 
(Fig.  518).  Others  have  completely  disappeared,  for  example, 
the  mammoth  and  mastodon,  with  whose  final  extinction  savac-e 
man  doubtless  had  something  to  do.  The  dodo,  a  large  running 
bird  in  the  island  of  Mauritius,  and  the  great  auk  (Fig.  505),  once 
so  common  along  the  northeastern  coast  of  America,  have  also 
been  exterminated.  The  eggs  of  the  auk  were  eaten  in  large 
numbers,  and  the  bird  itself,  which  was  unable  to  fly,  was  easily 
captured.  A  single  specimen  of  the  auk  or  its  egg  would  now 
bring  a  very  high  price,  for  most  large  museums  have  none. 


Fig.  516. —  Sheep  in  the  Scottish  Highlands.    A  thick  coat  of  wool  fits  these 
animals  to  endure  the  cold  of  a  northern  winter. 


Fia.  517.  —  Shetland  ponies,  so  protected  by  a  heavy  coat  of  hair  that  they 
thrive  in  the  raw  climate  of  the  Shetland  Islands. 


DISTRIBUTION  OF  ANIMALS.  365 

On  the  other  hand,  some  species  thrive  under  the  influence  of 
man.  For  example,  rats  and  mice  have  been  carried  all  over  the 
world  and  have  so  greatly  increased  as  to  become  a  pest ;  the 
English  sparrow,  introduced  into  America  from  Europe,  has  also 
become  a  nuisance ;  and  so  has  the  rabbit,  introduced  into  Australia. 
The  rabbit  destroys  the  food  needed  for  domesticated  animals, 
and  the  Australian  governments  have  been  obliged  to  take  up  the 
question  of  checking  its  further  spread.  Such  domesticated 
animals  as  sheep,  horses,  and  cattle,  have  had  their  range  so 
extended  that  they  are  now  found  in  all  quarters  of  the  earth. 

There  is  a  limit  to  man's  power  in  spreading  animals.  The 
camel  and  ostrich  might  be  transplanted  to  southern  California, 
but  they  cannot  be  made  to  thrive  in  New  England ;  the  elephant 
or  tiger  could  not  be  introduced  successfully  into  the  Arctic;  nor 
the  polar  bear  into  the  tropics.  Yet,  with  care,  man  has  been 
able  to  transplant  some  animals  into  all  kinds  of  climates. 

Summary.  —  Man  7ias  exterminated  some  species,  especially  the 
[  trger  ayid  more  defenseless  kinds,  and  has  greatly  reduced  the  mim- 
\'ers  of  many  others.  Under  his  influence,  other  animals  have  had 
their  range  greatly' increased ;  hut  there  is  a  limit  to  man's  power  of 
i\itroducing  animals  iyito  climates  for  which  they  are  not  7iaturally  fitted, 

242.  Domestic  Animals. — Man  has  been  very  successful 
in  adapting  animals  to  his  needs;  and,  by  so  doing,  he  has 
greatly  increased  his  own  prosperity.  To  have  a  horse  or 
buffalo  to  help  in  his  work,  or  sheep  or  hens  for  food,  adds 
greatly  to  a  man's  resources.  He  can  do  more  work  and  mak^i 
more  progress;  and  the  most  advanced  races  are  those  'v:th 
the  greatest  number  and  variety  of  domestic  animals. 

Some  animals  resist  efforts  at  domestication;  it  seems 
scarcely  possible,  for  example,  to  domesticate  the  lion.  Yet 
it  is  remarkable  how  large  a  number  of  animals  man  uses 
The  reindeer  of  northern  Europe  (Fig.  546)  is  used  as  a  draft 
animal  and  for  food  supply.  Eskimo  dogs  (Fig.  525),  which 
are  little  better  than  half-tamed  wolves,  are  of  great  service 
in-hunting  and  in  drawing  sledges  over  the  ice.  In  the  high- 
lands of  central  Asia  the  yak  is  domesticated;  the  buffalo 


866  NEW  PHYSICAL   GEOGRAPHY. 

(Fig.  520)  and  elephant  (Figs.  512,  521)  in  southern  Asia, 
and  the  camel  (Fig.  519)  in  the  arid  belts  of  Africa  and  Asia. 
Cats,  dogs,  horses,  cattle,  sheep,  goats,  and  pigs  are  domesti- 
cated all  over  the  world.  Among  domesticated  birds  are 
hens,  turkeys,  ducks,  geese,  and  doves. 

As  in  the  case  of  plants,  the  origin  of  many  of  these  is  not 
known ;  they  date  back  thousands  of  years,  long  before  the  first 
records  of  history.  It  is  a  striking  fact  that  the  ]Se\v  World  has 
supplied  only  two  domesticated  animals,  the  llama  of  South 
America  (Fig.  514)  and  the  turkey.  If  it  had  not  been  almost  ex- 
terminated, the  bison  probably  could  have  been  domesticated.  On 
several  ranches  in  the  West  there  are  now  small  herds  of  bison 
from  which  it  is  yet  possible  that  this  animal  may  be  domesticated. 

Summary.  —  WJdle  some  animals  resist  domestication,  man  has 
succeeded  in  adapting  many  mammals  and  birds  to  his  use,  either 
for  food  or  as  work  animals.  Of  these,  the  New  World  has  supplied 
only  two,  the  llama  and  turkey,  though  the  bison  may  yet  be  added. 

Topical  Outline  and  Review  Questions. 

Topical  Outline.  —  227.  Influence  of  Surroundings.  —  Air  ;  water* 
heat ;  cold ;  cold-blooded  animals ;  warm-blooded  animals ;  cause  of 
warmth. ;  protection ;  dependence  on  plants ;  sunlight ;  mode  of  life  , 
means  of  securing  food  and  escaping  enemies;  influence  of  gravity. 

228-  Animal  Life,  or  Fauna,  of  the  Arctic.  —  Animals  in  and  near 
the  sea;  sea  birds;  southward  migration;  land  birds;  mammals;  rep- 
tiles ;  insects ;  mammals  in  the  sea ;  protection  from  cold ;  white  color. 

..'?9,  Temperate  Fauna.  —  (a)  Mode  of  life:  open  plains;  forest; 
moui.  ^ins ;  arid  regions;  caverns;  underground;  nocturnal  animals. 
(b)  Common  animals :  variety  ;  birds ;  mammals ;  opossum ;  fur-bearing 
animals;  beaver. 

230.  Tropical  Fauna. — Plants;    insects;    birds;    reptiles;    mammals. 

231.  Desert  Fauna. — Contrast  with  humid  regions;  fauna  of  south- 
western United  States  ;  limit  of  food;  source  of  water;  the  camel. 

232.  Fresh-water  Faunas. —  Kinds;  illustrations;  difference  in  sur- 
roundings; temperature;  salt  lakes;  marine  animals  in  fresh  water. 

233.  Homes  of  Animals.  —  Invertebrates;  insects;  reptiles  and  am- 
phibia; birds;  »nammals. 

,     234.   Spread  of  Animals.  —  Reason  for  large  number  of  vounsf ;  uiipp> 


^g?ww;F^EWB^H9^PP>Ppe*?f» 


"WUPBT 


Fig.  518.  —  A  herd  of  bison.    These  animals  formerly  roamed  over  the  prairies 
and  plains  of  the  AVest  in  enormous  herds. 


Fig.  519.  —  A  cz^ravan  on  the  desert  of  Persia- 


FiQ.  520.  —  Asiatic  buttalo,  used  as  a  work  animal  in  southern  and  western  Asia, 
eastern  Europe,  and  northeastern  Africa. 


FiQ.  5'21.  —  The  elephant,  being  used  for  drawing  cocoanuts  from  a  cocoanut 

grove  in  Bouthern  Asia. 


DISTBIBUTIOJS    UJ^   ANIMALS,  '6\jl 

tected  young ;  protection  of  young ;  evolution;  reindeer;  elephants;  dis- 
tribution of  ocean  animals  ;  of  air  dwellers  ;  of  land  animals. 

235.  Barriers  to  the  Spread  of  Animals.  —  Water;  forest;  desert; 
mountain  ;  animals  that  easily  pass  barriers. 

236.  Island  Faunas.  —  (a)  Bermudas:  position;  plants;  animals. 
(h)  Means  of  reaching  islands:  currents;  flight;  wind;  birds  at  sea. 
(c)  Other  islands :  Azores;  Galapagos;  Hawaiian  Islands. 

237.  Australian  Fauna. —  (a)  The  animals:  birds;  monotremes;  mar- 
supials, (b)  Explanation :  former  distribution  ;  development  of  fierce 
enemies;  separation  of  Australia;  protection  by  ocean  barrier. 

238.  South  American  Fauna.  —  Peculiar  animals ;  explanation. 

239.  Faunas  of  Other  Continents. — Resemblance  in  northern  lands; 
in  Africa  and  southern  Asia;  explanation. 

240.  Zones  of  Animal  Life. —  The  zones;  names;  cause;  boundaricvS. 

241.  Influence  of  Man.  —  (a)  Man  as  an  enemy :  cause  for  destruction  ; 
general  result ;  bison;  mammoth  and  mastodon;  dodo;  auk.  {Ji)  Influ- 
ence in  spreading  animals :  rats  and  mice ;  English  sparrow  ;  rabbit ; 
domestic  animals,     {c)   Limit  to  influence  ;  examples. 

242.  Domestic  Animals.  —  Importance ;  instances  of  domesticated 
mammals;  birds;  New  World  animals ;  bison. 

Review  Questions.  —  227.  What  is  the  dependence  of  animals  on 
air,  water,  and  temperature?  By  what  means  is  cold  endured?  What 
is  the  difference  in  the  blood  of  animals?  Why  are  animals  dependent 
on  plants  for  food  ?  Why  are  they  not  dependent  on  sunlight?  In  what 
positions  do  animals  live?  How  are  they  fitted  to  secure  food  and 
escape  enemies?     State  the  influence  of  gravity  on  the  body. 

228.  AVhat  is  the  nature  of  Arctic  bird  life  ?  What  is  the  condi- 
tion of  life  on  land  ?  What  warm-blooded  animals  live  in  the  sea?  How 
are  Arctic  animals  protected  from  the  cold?     What  about  their  color? 

229.  Under  what  different  conditions  do  temperate  animals  live? 
Name  some  of  the  common  birds.     Mammals.     Fur-bearing  mammals. 

230.  W^hy  are  animals  so  abundant  in  the  tropical  zone  ?  What  is 
the  condition  of  insect  life  there?     Birds?     Reptiles?     Mammals? 

231.  Contrast  desert  and  tropical  forest  faunas.  What  animals  are 
found  in  the  desert  of  southwestern  United  States?  Why  are  there  so 
few  ?   How  do  they  secure  water?    How  is  the  camel  adapted  to  desert  life  ? 

232.  What  kinds  of  animals  live  in  fresh  water?  How  do  the  faunas 
differ?     How  may  marine  animals  come  to  live  in  fresh  water? 

233.  In  what  situations  do  invertebrates  live?     The  higher  groups? 

234.  In  what  way  is  the  spread  of  animals  made  certain?  Give 
illustrations  of  evolution.  What  kinds  of  animals  are  most  widespread? 
Why  ?     What  about  land  animals'^ 


368  iN^^^  PHYSICAL   GEOGRAPHY. 

235.  What  barriers  are  there  to  the  spread  of  animals  ?  What  kinds  of 
animals  most  easily  overcome  them  ? 

236.  What  is  the  nature  of  the  Bermuda  plant  and  animal  life  ?  How- 
has  this  life  reached  the  islands  ?     What  is  the  condition  in  other  islands  ? 

237.  What  are  the  peculiarities  of  life  in  Australia  ?     Explain  this. 

238.  What  does  the  South  American  fauna  indicate  ? 

239.  What  is  indicated  by  the  faunas  of  other  continents  ? 

240.  What  are  the  reasons  for  the  zones  of  life?  Name  the  realms. 
Name  the  regions  of  the  northern  realm  (Fig.  515). 

241.  Why  is  man  an  enemy  of  many  animals  ?  Give  illustrations  of 
his  influence  in  extermination.  In  increasing  the  range  of  animals.  How 
is  his  power  limited  in  this  respect? 

242.  Of  what  advantage  are  domestic  animals?  Give  instances  of 
domestic  animals  in  various  parts  of  the  world.  What  domestic  animals 
has  the  New  World  supplied?     What  about  the  bison ? 

Suggestions. —  No  special  suggestions  are  made  for  this  chapter, 
largely  because  of  the  difficulty  of  offering  suggestions  adapted  to  large 
numbers  of  schools.  Yet  a  teacher  especially  interested  in  this  phase  of 
the  subject  will  find  opportunity  for  illustrative  work,  —  with  books, 
pictures,  specimens,  and  museums,  if  in  a  city ;  in  the  field,  if  in  the 
country. 

Reference  Books.  —  Wallace,  Island  Life,  Macmillan  Co.,  New  York, 
1892,  81.75  ;  Geographic  Distribution  of  Animals,  Harper  Bros.,  New  York, 
1876,  -flO.OO;  Heilprin,  Dlstrlhution  of  Animals,  Appleton  &  Co.,  New 
York,  1886,  $2.00;  Beddard,  Zoogeographij,  Macmillan  Co.,  New  York, 
1895,  $1.50;  Lydekker,  Geographical  History  of  Mammals,  Macmillan  Co., 
New  York,  1896,  $2.60;  Le  Conte,  Evolution,  Appleton  &  Co.,  New 
York,  1891,  $1..50 ;  Jordan,  Factors  in  Organic  Evolution,  Ginn  Sc  Co., 
Boston,  1894,  $1.25. 


CHAPTER  XIX. 

MAN    AND    NATURE. 
DEVELOPMENT   OF    MANKIND. 

243.  Early  Man.  —  What  sort  of  life  people  lived  before 
they  Avere  sufficiently  enlightened  to  leave  any  written 
records,  we  can  judge  only  by  the  records  of  their  deeds  as 
shown  in  mounds,  monuments,  drawings,  utensils,  weapons, 
and  other  relics,  and  by  comparison  with  other  uncivilized 
people  of  the  present  day.  Written  records  tell  us  much 
about  our  ancestry  during  the  last  two  or  three  thousand 
years.  For  example,  when  the  Roman  Empire  was  develop- 
ing, the  Germans  and  English  were  rude  savages;  and  still 
earlier,  the  inhabitants  of  the  Italian  Peninsula  were  in  the 
same  condition.  To-day,  both  in  the  Old  and  the  New 
World,  there  are  races  that  have  not  yet  risen  above  savagery. 

The  study  of  human  development  through  labor  and 
thought  is  most  interesting,  even  though  there  are  many 
gaps  that  can  be  filled  only  by  the  use  of  reason  and  imag- 
ination. Ever  since  man  has  been  compelled  to  earn  his 
bread  by  the  sweat  of  his  brow,  the  brightest  men  have 
sought  to  conquer  nature  and  modify  their  environment  by 
the  use  of  their  wits.  Steadily  through  the  centuries  mon 
has  acquired  useful  knowledge  from  experience ;  and,  as  a 
result  of  his  efforts,  modern  civilization  enjoys  many  advan- 
tages, comforts,  and  conveniences  over  savage  and  semi- 
civilized  people. 

Summary.  —  But  little  is  known  of  man's  early  ancestry.  Through 
labor  and  thought  he  has  made  wonderful  j^rogress  in  civilization. 

244.  Dependence  of  Man  on  Nature.  —  Even  the  most  civi- 
lized men  are  dependent  on  nature,  as  animals  and  plants  are. 
Man  must  have  air  to  breathe,  water  to  drink,  and  food  to 
eat.  Furthermore,  his  sight  depends  on  sunlight,  and  his 
speech  and  hearing  on  sound  waves,  transmitted  through  the 

In  369 


SlO  NEW   PHYSICAL    GEOGRAPBY, 

air.     If  his  liome  is  in  a  cool  climate,  lie  must  have  clothing 
and  shelter ;   and  he  obtains  materials  for  these  from  nature. 

In  these  respects  both  savages  and  civilized  men  are  dependent 
on  nature ;  but  to  live  as  civilized  men  do,  we  must  rely  on  other 
things  as  well.  For  warmth  and  light  we  depend  on  coal  and  oil ; 
for  manufacturing,  upon  coal  and  water  power;  for  transportation, 
upon  coal  and  wind;  for  communication,  upon  electricity;  for  many 
objects  of  daily  use,  upon  mineral  substances.  The  resources  of 
the  world  are  drawn  upon  by  civilized  nian,  and  his  powers  have 
so  developed  that  he  has  learned  to  adapt  to  his  needs  many  of 
the  products  and  forces  of  nature.  Each  year  his  ability  to 
do  this  increases.  In  this  respect  man  has  risen  immeasurably 
above  all  other  forms  of  life. 

Summary.  —  All  men  depend  on  nature  for  car,  icater,  and  food  ; 
and  civilized  man  is  dependent  for  many  other  things.  Each  year 
he  is  learning  better  how  to  make  use  of  nature. 

245.  Food  Supply.  —  Man  began  his  conquest  of  nature 
because  of  the  need  of  food.  The  steam  engine,  the  factory, 
and  wireless  telegraphy  are  the  climax  of  a  series  of  inven- 
tions which  began  when,  to  the  teeth  and  claws  with  which 
animals  secure  food,  man  added  simple  implements. 

By  using  stone  implements,  such  as  spear  and  arrow  points, 
hammers,  and  hatchets ;  by  fashioning  wood  for  handles  and  for 
bows;  and  by  making  simple  hooks  for  fishing,  early  man  greatly 
increased  his  ability  to  obtain  animal  food.  Even  to  this  day, 
savage  races  make  use  of  such  primitive  implements  (Fig.  522). 

As  an  important  source  of  food,  primitive  man  made  use 
of  plants,  especiall}^  the  seeds,  fruits,  bulbs,  and  roots. 
The  mandioca,  sweet  potato,  potato,  yam,  plantain,  banana, 
cocoanut,  date,  and  the  grains,  including  wheat,  barley,  rye, 
corn,  rice,  and  millet,  are  among  the  leading  plant  foods.  To 
gather  these,  scattered  as  they  are  in  nature,  required  much 
work,  and  early  man  naturally  found  it  profitable  to  plant 

k 


Fig.  522.  —  Philippine  natives,  showing  how  little  clothing  is  necessary  in  such 

a  hot  climate. 


Fia.  523.  —  Laplanders  dressed  in  luis.     Contrast  with  Fig.  522. 


Fio.  n'Ji       Kskimo  women  at  Cape  York,   Greenland. 

summer  tuple,  or  skin  tent. 


Behind  tiiem  '■<«  the 


MAN  AND  NATURE,  61  \ 

and  vjdre  for  them.     Simple  spades  and  hoes,  at  first  made 
of  stone  or  wood,  aided  greatly  in  this  work. 

By  domesticating  plants  (p.  348)  and  animals  (p.  365)  a 
great  addition  was  made  to  man's  resources.  Domestica- 
tion is  the  basis  of  civilization,  for  it  gave  man  the  habit  of 
working,  of  storing  up  for  a  season  of  need,  and  of  trading  ; 
upon  it  also  depends  the  idea  of  property  and  of  the  home. 

To-day  all  the  world  depends  for  food  on  the  farmer  and 
herder.  Wherever  conditions  favor,  the  land  is  cleared  for 
farming,  and  the  majority  of  mankind  are  engaged  in  the  pro- 
duction of  food  for  themselves  or  for  those  with  a  different 
occupation.  The  plow,  the  reaper,  and  the  threshing  machine 
have  taken  the  place  of  the  primitive  spade  and  hoe.  Thousands 
of  railway  cars  and  vessels  are  constantly  engaged  in  moving 
products  of  the  faiirs  to  places  where  men  are  engaged  in  other 
pursuits,  or  where  the  population  is  too  dense  to  permit  the  pro- 
duction of  all  the  food  needed.  Agriculture  is  by  far  the  most 
important  of  industries. 

Summary.  —  Tlie  devising  of  simjyle  ifniplemeyits  for  securing  i^Uutt 
and  aniynal  food  is  the  basis  of  modem  invention.  Tlie  domesti- 
cation of  pUuds  and  animals  for  food  is  the  basis  of  our  civiliza- 
tion. All  the  v'orld  depends  for  food  on  the  farmer  and  herder,  and 
agriculture  has  become  the  most  important  of  industries. 

246.  Clothing.  —  In  a  hot  climate  man  has  little  need  for 
clothing  (Fig.  522)  ;  but  in  a  cool  or  cold  climate  some  pro- 
tection is  necessary.  Without  it  man  could  not  occupy  the 
cold  temperate  zane.  Various  natural  products,  including 
skins  (Fig.  523),  wool,  and  plant  fibers,  have  been  used  to 
protect  the  body.  Early  Germans  and  Britons  were  clothed 
in  skins,  as  the  Eskimos  are  to-day  (Figs.  524,  525). 

In  cold  climates  one  of  the  objects  of  hunting  has  always  been 
to  secure  materials  for  clothing ;  and  one  of  the  objects  of  herd- 
ing is  the  production  of  wool  and  leather,  and  of  farming,  the 
production  of  fibers  for  cloth.  The  principal  vegetable  fibers 
used  for  making  cloth,  rope,  etc.,  are  cotton,  flax,  hemp?  and  jute. 


372 


NEW  PHYSICAL   GEOGRAPHY. 


Wool,  silk,  furs,  and   leather   are   animal   products,  at   present 
widely  used  by  civilized  people  for  clothing. 

The  production  and  manufacture  of  materials  for  clothing  now 
.»ank  among  the  great  industries  of  the  world.  The  fact  that  the 
most  civilized  races  live  in  the  cool  temperate  zones  makes  the 
production  of  materials  for  clothing  far  more  important  than  if 
their  homes  were  in  the  tropical  zone. 

Summary.  —  Clothing  is  needed  by  all  dwellers  in  cool  climates, 
and  for  it,  various  animal  and  plant  j^roducts  are  used.  Since  the 
most  civilized  races  live  in  the  cool  temperate  zones,  the  production  and 
manufacture  of  clothing  are  among  the  most  impjortant  of  industries. 

247.  Shelter.  —  Man  has  adopted  many  devices  for  securing 
shelter  from  the  elements.     The  summer  home  of  the  Eskimo 

is  a  skin  tuple 
[  ^{g.  524)  ;  his 
winter  home  a  hut, 
or  igloo,  of  snow 
or  ice  (Fig.  525). 
Indian  wigwams 
were  made  of 
skins.  The  nom- 
ad of  the  deserts 
uses  skins  and 
blankets  (Fig. 
526)  made  of  the 
wool  of  his  domes- 
tic animals.  Sod 
houses  are  still 
built  in  many  regions.  Grass  huts,  and  branches  woven  into 
a  simple  shelter  (Fig.  529),  are  common  in  the  tropical  zone; 
and  some  savages  live  there  with  hardly  any  shelter.  In  parts 
of  Europe  and  southwestern  America,  caves  and  overlianging 
ledges  furnished  shelter  to  primitive  man. 

Long  before  the  historical  period,  clay  and  wood  were 
used,  at  first  very  crudely,  as  materials  for  building  perm«- 


FiG.  525.  —  Eskimo  winter  home,  or  igloo.  Eutrauce 
is  by  way  of  a  small  ice  tunnel,  through  which 
wind  does  not  easily  enter. 


i^^^w^^^J^l^lpllJw^»l^[^l^^^j^l^^WM»liM«,w^MlP!W^;pJw^yw.'l '  '.m 


Fig.  526.  —  A  tent  of  blankets  used  for  shelter  by  nomads  on  the  desert  of  Sahara. 


Fig.  .527.  — Thatched  house  in  the  Philippine  Islands,  needed  for  protection  from 
sun  and  rain,  not  cold.  It  is  raised  above  the  ground  to  avoid  dampness 
and  to  prevent  the  entrance  of  animal  pests,  which  are  very  troublesome. 


MAN  AND   NATURE. 


3^8 


nent  homes.  The  use  of  wood  began  in  forest  regions  (Fig. 
528),  at  first  doubtless  by  the  use  of  boughs,  branches,  and 
logs  ;  then  of  rough-hewn  boards.  Simple  log  cabins,  some 
of  which  still  remain,  were  built  by  pioneers  in  America. 

Stone  houses 
were    probably  ^ 

first  made  by 
merely  piling 
stones  together,  as 
is  done  to-day  by 
the  Cape  York 
Eskimos.  Then 
mud  was  used  to 
fill  the  cracks,  and 
later,  mortar  was 
employed.  The 
first  use  of  clay 
was     in     makinsf       ^       ^  ,  .  ,     ^ 

.  1-1  Fig.  529.  —  A  negro  village,  the  huts  being  made  of 

SUn-Ciriecl      bricks,  woven  branches,  a  very  simple  form  of  shelter. 

or  adobe,  still  em- 
ployed in  arid  countries,  as  the  Holy  Land,  Spain,  and  New 
Mexico.  These  are  too  easily  affected  by  dampness  for  use 
in  moist  climates ;  but  the  discovery  of  how  to  bake  bricks 
by  fire  has  made  the  use  of  clay  possible  there.  In  arid 
regions,  where  trees  are  scarce  or  absent,  stone  and  sun- 
dried  bricks  are  very  widely  used. 

Our  fine  wood,  brick,  and  stone  houses  have  been  developed,  by 
a  series  of  improvements,  from  these  simple  beginnings. 

The  cold  of  winter  calls  for  further  protection  than  that  fur- 
nished by  clothing  and  houses.  Fire  supplies  this,  and  it  is  safe 
to  class  the  use  of  fire  among  the  greatest  of  human  discoveries. 
It  has  become  of  value  not  merely  for  heating,  lighting,  and  cook- 
ing, but  as  the  basis  for  much  of  our  modern  manufacturing.  It 
has  led  to  mining  of  coal,  production  of  oil  and  gas,  mining  and 
manufacturing  of  iron,  and  many  other  industries.     As  a  re^^ult 


374 


NEW  PHYSICAL   GEOGRAPHY. 


of  its  use,  modern  man  has  come  to  count  as  necessities  hundreds 
of  articles  about  which  primitive  man  knew  nothing. 

Summary.  —  Menu/  primitive  means  have  been  employed  for  secur- 
ing shelter ;  for  example,  skins,  snow,  blankets,  grass,  branches,  and 
caves.  Tlie  use  of  wood,  stone,  and  clay  doubtless  started  in  a  very 
primitive  way :  wood  from  the  use  of  boughs  and  logs;  stone  from 
mere  piles ;  aud  clay  in  the  form  of  sun-dried  brick.  The  discovery 
of  fire  has  been  of  great  importance,  making  2)ossible  manufacturing 
and  thus  opening  to  man^s  use  many  otherwise  itseless  matericds. 

248.  Selection  of  Homes.  —  Doubtless  early  man  had  no 
fixed  home,  but  wandered  about  in  search  of  food,  as  many 

primitive  peoples  do  to- 
day. When  for  any 
reason  a  home  became 
desirable,  two  consider- 
ations led  to  the  selec- 
tion of  a  location  : 
(1)  nearness  of  food 
supply;  (2)  protection 
from  enemies.  Homes 
are  still  located  by  large 
numbers  of  people  with 
the  first  idea  in  mind  : 
for  example,  farmers, 
fishermen  (Fig.  533), 
and  hunters  ;  but,  for- 
tunately, civilized  men 
are  no  longer  obliged 
to  take  account  of  the 
second. 


Fig.  530.  —  Native  houses  iu  trees,  New 
Guinea. 


There  are  many  illustrations  of  the  location  of  houses  on  sites 
that  give  protection  from  enemies.  Some  savages  build  houses  in 
trees  (Fig.  530),  and  some  on  piles  in  water  (Fig.  534),  as  the 
ancient  lake  dwellers  of  Switzerland  did.     The  Pueblo  Indians 


lA.^ 


Fig.  531.  —  An  Indian  pueblo  in  Arizona,  on  tlie  top  of  a  mesa,  j^nd  overlooking 
the  surrounding  country.     The  steep  face  is  difficult  of  access. 


Fto.  .^;i2.  —  Ruin  (on  the  ri^^^t)  of  a  castle  on  the  Rhine,  built  iu  a  position  fairly 

safe  from  attack 


Fia.  533.— Housjs  built  ou  a  steep  hillside  in  a  inoimtaiuous  peninsula  soi^^tli 
of  Naples,  Italy.     A  few  spots  on  the  slope  are  cultivated,  but  most  of  the 
laud  is  unfit  for  cultivatior      Thf.  bouse,,  art,  however,  uea,i  tLt,  wat« 
and  fisJiing'  is  poH«i>»i 


MAN  AND  NATURE. 


376 


New  Guinea  village,  built,  for  protection, 
on  piles  in  the  water. 


lived  on  top  of  steep-sided  buttes  and  mesas  (^ig.  531)  ;  others 

lived  in  caves  and  under  overhanging  ledges  on  cliff  sides  (p.  -85). 

Gastles    in    Europe 

were  often  built  on 

hills,      and      other 

places    difficult    of 

access    (Fig.    532) ; 

and,      for     further 

protection,      strong 

walls     were     built 

around  them. 

Summary.  —  TJie 
homes  of  ijrimitive 
m  a  n  have  been 
selected  vnth  refer-  Fig.  534. 
ence  to  nearness  of 
food  and  possibility 

of  protection  from  enemies.     For  the  sake  of  j^rotection,  homes  have 
been  located  in  trees,  in  the  water,  on  cliff'  sides,  and  on  hills. 

249.  Location  and  Growth  of  Cities.  —  When  scattered  it 
is  easier  for  men  to  secure  sufficient  food  than  when  many 
live  in  a  single  place  ;  but  it  is  less  easy  to  ward  off  the 
attacks  of  enemies.  Largely  for  this  reason,  the  custom  has 
grown  for  men,  even  savages  (Figs.  529,  530,  534),  to  gather 
into  communities.  From  their  villages,  these  primitive  peo- 
ple go  out  to  the  neighboring  fields,  forests,  and  waters  for 
farming,  hunting,  or  fishing,  and  yet,  being  near  togetlier, 
are  ready  to  resist  attack.  They  are  also  ready  for  an  ex- 
pedition to  attack  a  neighbor  for  revenge  or  profit. 

The  leader  in  attack  or  defense  easily  became  chief  of  the 
nllage ;  if  powerful  enough,  he  might  become  ruler  of  several 
villages.  Even  at  present  nations  grow  in  power  and  territory 
by  conquering  weaker  peoples.  Government  has  become  very 
complex,  and  differs  greatly  among  nations ;  but,  like  all  our 
wonderful  modern  life,  it  had  its  beginnings  in  the  simple  prac- 
tices of  our  early,  uncivilized  ancestors. 


376  NEW  PHYSICAL   GEOGRAPHY, 

Many  European  towns  grew  np  because  of  the  need  of 
defense.  One  man,  more  powerful  tlian  tlie  rest,  built  a 
strong  stone  castle,  perhaps  on  a  hill,  and  protected  the 
region  about  it  by  a  wall.  Farmers,  soldiers,  and  others, 
under  the  protection  of  tlie  castle  owner,  worked  for  him, 
lived  in  houses  within  the  walls,  and  helped  defend  them 
when  attacked.  In  Europe,  hundreds  of  places  like  this  are 
still  to  be  seen,  although  no  longer  used  for  defense.  Around 
some,  with  favorable  situations,  large  cities  have  developed. 

In  locating  cities,  at  present,  there  is  no  need  of  consider- 
insr  defense.  The  ^reat  cities  of  the  civilized  world  are  the 
capitals  of  large  nations,  and  the  busy  manufacturing  and 
commercial  centers.  London,  Paris,  Berlin,  Vienna,  Brus- 
sels, St.  Petersburg,  Madrid,  Rome,  Constantinople,  and 
other  large  Euro[)ean  cities  are  capitals.  The  first  five  are 
also  manufacturing  centers  ;  and  London,  Paris,  St.  Peters- 
burg, and  Constantinople  are  able  to  carry  on  commerce  by 
sea.     Each  of  these  cities  has  a  location  favorable  to  growth. 

All  flourishing  cities  in  the  world,  whether  great  or  small, 
owe  their  prosperity,  in  large  part,  to  their  favorable  situa- 
tion. Some,  like  Milan  in  Italy,  and  Vienna  in  Austria, 
are  situated  where  routes  of  travel  converge  or  cross.  They 
had  their  beginning  long  before  the  days  of  railways  ;  but 
the  railway,  making  them  centers  of  modern  traffic,  has 
greatly  increased  their  prosperity.  Many  cities,  like  Cincin- 
nati, St.  Louis,  Vienna,  and  Paris,  are  on  rivers  ;  and  others, 
like  Buffalo  and  Chicago,  are  on  large  lakes.  Still  others, 
like  Genoa,  Liverj)ool,  San  Francisco,  and  New  York,  are 
seaports.  Such  seaports  as  London,  New  York,  Philadelphia, 
Baltimore,  and  New  Orleans,  which  are  at  the  mouths  of 
rivers  that  open  pathways  into  the  interior,  have  exceptionally 
favorable  situations. 

Many  cities,  like  Lowell,  Lawrence,  and  Rochester,  owe  thei\ 
growth  to  water  power,  which  has  enc^ouraged  manufacturing. 
Others,  like  Scran  ton,  Wilkes  Barre,  Pittsburg,  and  Denver,  owe 


MA^r  AND  NATURE.  377 

their  development  mainly  to  near-by  mines.  Can  you  mention  other 
instances  of  cities  whose  growth  depends  on  their  favorable  loca- 
tion ?     What  has  helped  determine  the  growth  of  your  own  city  ? 

Summary.  —  Tlie  tendency  of  peoj^le  to  congregate  in  centers  had 
its  origin  in  the  need  of  defense,  and  from  it  has  arisen  government. 
Some  large  European  toums  grew  around  fortified  castles ;  hut  the 
largest  have  prospered  either  because  they  are  capitcds  of  great  nations 
or  are  manufacturing  and  commercial  centers.  Flourishing  modf^rn 
cities  are  mainly  located  on  one  of  the  following  sites :  at  the  crossing 
of  trade  routes ;  07i  rivers,  especially  at  their  mouths ;  on  har- 
bors;  on  lake  shores  ;  near  water  poicer  ;  near  mines. 

250.  Development  of  Commerce.  —  Even  primitive  men 
desire  articles  which  they  cannot  produce.  For  example, 
remote  Eskimo  tribes  will  gladly  exchange  skins  for  pieces 
of  wood ;  and  central  African  negroes  will  trade  ivory  for 
simple  trinkets.  Two  ways  of  obtaining  desired  objects  are 
open  :  one  to  seize  them,  the  other  to  give  articles  in  exchange 
for  them  ;  and  both  methods  are  resorted  to.  From  exchange, 
commerce  has  developed. 

Objects  of  trade  were  early  carried  overland,  at  first  on 
foot,  later  by  the  aid  of  animals,  even  across  deserts  and 
mountains.  The  first  commerce  by  sea  was  carried  on  in 
small,  open  boats,  propelled  by  oars;  later,  sails  were  used. 
Even  before  Bible  times,  and  before  Europeans  became  civi- 
lized, caravans  crossed  the  deserts  of  Asia  Minor,  bringing 
treasures  from  Asia.  The  inclosed  Mediterranean  offered 
opportunity  for  the  extension  of  this  commerce  by  sea  ai:d 
for  the  introduction  of  Asiatic  civilization  along  its  shores. 

A  powerful  nation  developed  on  the  Grecian  peninsula, 
and  its  irregular  coast  bred  a  race  of  sailors.  Even  to-day 
the  Greeks  are  the  sailors  of  the  Mediterranean.  The 
ancient  Greeks  carried  their  commerce  to  all  parts  of  the 
Mediterranean,  establishing  colonies  which  later  developed 
into  powerful  independent  nations.  As  the  boats  were  made 
larger,  the  commerce  which  developed  among  Mediterranean 


378 


NEW  PHYSICAL   GEOGRAPHY. 


nations  was  gradually  extended  into  the  open  ocean,  and 
even  up  the  Euroj^ean  coast  to  the  British  Isles.  The  Medi- 
terranean may  be  called  the  cradle  of  early  navigation. 

When  the  Mohammedans  interfered  with  trade  between 
Europe  and  Asia,  a  sea  route  to  India  was  sought.      The 

Portuguese  found 
one  around  Africa, 
and  Columbus,  in 
searching  for  one 
toward  the  west, 
discovered  Amer- 
ica. For  the  de- 
velopment of  these 
new  lands,  and  the 
valuable  com- 
merce with  them, 
ships  were  made 
still  larger  and 
stronger.  Then 
came  the  use  of 
steam ;  and  now 
huge  steel  ships 
carry  the  increasing  commerce  of  the  world  over  all  oceans. 

Commerce  was  once  carried  on  by  actual  exchange  of  goods, 
and  in  some  cases  this  is  still  done.  But  a  far  better  way  is  to 
have  some  medium  of  exchange.  Such  a  medium  is  money. 
The  use  of  money  is  far  simpler  than  direct  exchange.  For  ex- 
ample, a  man  who  needs  shoes  might  hnd  it  difficult  to  get  them 
if  he  had  only  his  labor  to  offer;  but  if  he  receives  money  for 
his  labor,  he  can  get  what  he  needs.  Any  substance  that  has 
a  recognized  and  fairly  nniform  value  could  be  used  as  money. 
Gold  is  generally  used,  because  it  is  not  too  common,  is  not  easily 
destroyed,  and  is  valued  by  all  peoples  for  ornament. 

Commerce  has  aided  greatly  in  the  spread  of  civilization,  for  it 
has  brought  people  into  closer  communication  and  sympathy  with 


Fig.  535.  —  The  Suez  Canal.  The  neck  of  land  which 
separates  the  Mediterranean  and  Red  seas  forced 
those  who  sought  a  water  route  to  India,  four  or 
five  centuries  ago,  to  undertake  the  explorations 
which  led  to  such  important  discovei'ies.  The 
demands  of  modern  commerce  for  a  shorter  water 
route  between  Europe  and  Asia  led  to  the  con- 
struction of  the  Suez  Canal. 


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Fig.  539.  —  Bridge  across  the  Firth  of  Forth,  near  Edinburgh,  Scotland.  This 
bridge,  like  many  others,  was  buiii  to  accommodate  the  increasing  modern 
commerce. 


f^ifc.  540. — Bhlpplnv  tn  N^w  v»»'»  Haitwr. 

behind  the  ouuitir 


Brooklyn  Brlrtg* 


MAN  anb  nature.  379 

one  another,  and  has  made  peo'ple  in  one  section  learn  from  those 
in  another.  As  a  means  of  commnnication,  writing  has  developed, 
and,  like  other  features  of  our  civilization,  this  has  been  evolved 
from  simple  beginnings.  For  example,  picture  writing,  or  recording 
events  by  symbols  carved  on  wood  or  stone,  has  been  used  by  many 
primitive  peoples  (Fig.  538).  From  this  the  alphabet  developed, 
then  printing,  which  has  proved  so  important  an  aid  in  spread- 
ing knowledge.  The  telegraph,  ocean  cable,  and  telephone,  made 
possible  by  the  use  of  electricity,  have  now  brought  all  parts  of 
the  civilized  world  in  close  touch  with  one  another.  Wireless 
telegraphy  is  the  last  great  advance  in  commanication.  It  is  part 
of  the  progress  of  the  human  race  toward  higher  and  higher 
civilization,  in  which  commerce  has  had  so  great  an  influence. 

Summary.  —  Commerce  has  developed  from  simple  exchange  car- 
ried on  among  primitive  peop)le,  at  first  overland,  either  on  foot  or  by 
the  aid  of  animals,  and  on  the  sea  by  the  use  of  boats  propelled  by  oars. 
Early  commerce  betiueen  Asia  and  Europe,  overland  across  Asia 
Minor,  and  thence  in  the  inclosed  icaters  of  the  Mediterranean,  made 
the  Mediterranean  the  cradle  of  navigation.  The  discovery  of  a 
luater  route  to  Asia,  and  of  the  Neia  World,  resulting  from  the  clos- 
ing of  routes  to  Asia  by  the  Mohammedans,  have  led.  to  the  develop- 
ment of  larger  ships  and  to  the  great  advances  of  modern  commerce. 
The  use  of  money,  the  extension  of  civilization,  the  development  of 
loriting  and  printing,  and  communication  by  electricity  are  among 
the  important  outcomes  of  the  development  of  commerce. 

251.  Influence  of  Man  on  Nature.  — In  his  progress,  man  has  in 
many  ways  profoundly  influenced  his  surroundings.  He  has 
modified,  extended,  and  destroyed  plants  (pp.  348,  349)  and  ani- 
mals (pp.  364,  365).  By  removing  the  forest  he  has  made  it  pos- 
sible for  water  to  run  off  more  rapidly  (p.  50),  washing  soil  into  the 
streams  and  causing  great  variations  in  river  volume.  A.s  a 
result,  some  streams  formerly  useful  for  water  power  are  now  too 
variable ;  and  some  areas,  as  parts  of  Italy,  France,  and  Missis- 
sippi, have  had  their  soil  stripped  off,  leaving  either  bare  rock  or 
a  surface  too  badly  gullied  for  farming  (p.  51). 

On  densely  settled  floodplains  and  deltas,  the  river  courses 
have  been  controlled  and  annual  floods  prevented.     Stream  courses 


380  NEW  PHYSICAL   GEOGRAPHY. 

have  been  straiglitened  and  deepened  for  navigation,  and  canals 
dug  around  rapids,  and  from  ocean  to  ocean.  For  use  in  irri- 
gation, river  water  has  been  led  over  arid  lands ;  and  lakes  and 
ponds  have  been  formed  to  secure  steady  water  supply  for  irriga- 
tion and  for  other  purposes.  Each  of  these  acts  of  man  inter- 
feres with  natural  conditions. 

Along  the  seacoast,  walls  are  built  to  check  the  work  of  the 
waves.  To  better  lit  them  for  shipping,  harbors  and  channels  are 
dredged;  jetties  and  sea  walls  are  built  to  prevent  currents  from 
closing  harbor  mouths  with  sand  bars ;  and,  by  building  break- 
waters, harbors  are  actually  made  by  artificial  means. 

Much  change  is  made  on  the  dry  land  also.  The  ground  is  pierced 
with  wells  for  water,  oil  (Fig.  542),  and  gas,  and  these  substances 
are  led  to  the  surface.  In  the  removal  of  coal,  iron,  and  other 
mineral  products,  the  strata  are  honeycombed  with  shafts  and  tun- 
nels (Fig.  541) ;  and  in  quarrying,  and  in  removing  clay  and  sand, 
hills  are  lowered  and  deep  pits  made.  Tunnels  are  dug  through 
mountains  (Fig.  186)  and  deep  cuts  made  in  hillsides,  while  great 
embankments  are  built  of  the  rock  removed.  Earth  and  rock  are 
removed  in  making  roads  and  in  digging  cellars ;  and,  over  great 
areas,  the  soil,  by  being  loosened  and  overturned  in  plowing,  is 
exposed  to  the  weather. 

These  are  some  of  the  ways  in  which  man  is  at  work  overcom- 
ing obstacles  which  nature  has  placed  in  the  way  of  his  advance. 
Civilized  man  brooks  no  obstacle  ;  he  removes  it  where  necessary ; 
he  is  everywhere  at  work  modifying  nature  to  serve  his  needs ; 
and  he  is  utilizing  his  surroundings,  and  the  forces  of  nature,  to 
help  in  his  onward  march  toward  higher  civilization.  In  this 
respect  man  stands  apart  from  all  other  forms  of  life. 

Summary.  - //v  <i  niuUittule  of  2vat/s  man  is  influencing  nature: 
(leatrot/itif/,  niod/fi/iiK/,  or  extending  the  range  of  animals  and  plants  ; 
removing  the  fon^st,  thns  allowing  the  rain  to  run  off'  rapidly  and 
carry  aicay  the  soil ;  changing  or  conlrolling  streams;  improrlng  or 
making  ivaterivays ;  forming  lakes ;  interfering  with  the  natural  action, 
of  oceanic  agencies ;  boring  into  the  earth  and  removing  materials; 
and  exposing  soil  and  rock  to  the  iveather.  In  fact,  he  is  overcoming 
ull  obstacles  and  makiiig  nature  serve  his  needs. 


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■>*■---'■-■ 

'r"-*r—  ' 


Ftg.  541.  —  A  coal  mine  at  Shenandoah  City,  Pa.  Here  the  ground  is  honeycombed 
with  shafts  and  tunnels,  and  vast  quantities  of  coal  are  removed,  together 
with  associated  rock,  great  piles  of  which  are  seen  near  the  buildings. 


■-.>.  .  .  trv  .T^^gtr-Mm 


imUJtf  >■■;'<"! 


Fig.  542. Each  of  these  derricks  marks  the  site  of  a  boring  for  oil  at  Tidi-""*** 

Pa.   in  1870.    From  these  wells  large  amounts  of  oil  were  obtained 


MAN  AND  NATURE.  381 


DISTRIBUTION   OF   MANKIND. 


252.  The  Spread  of  Man.  —  During  the  development  of 
man,  as  outlined  above,  he  has  migrated  to  almost  all  lands. 
Starting  from  some  common  center,  he  spread  slowly,  guided 
by  the  same  laws  as  animals,  and  influenced  by  the  same  bar- 
riers. But  man's  superior  intelligence  has  permitted  him  to 
spread  farther  than  any  species  of  animal,  and  to  adapt  him- 
self to  all  climates.  Even  as  a  savage  he  reached  every  con- 
tinent and  most  oceanic  islands.  The  use  of  boats  aided 
him  in  crossing  the  ocean  barrier;  and,  by  means  of  clothing 
and  shelter,  he  has  overcome  the  barriers  of  cold  climates. 

The  spread  of  man  has  been  in  part  a  slow,  steady  advance 
outward  in  all  directions,  as  in  the  case  of  animals,  and  in 
part  a  rapid  migration  in  large  numbers.  It  was  such  rapid 
spread  that  led  to  the  building  of  the  great  Chinese  wall  (Fig. 
543)  as  a  barrier  to  the  hordes  that  moved  outward  from 
central  Asia.  Similar  hordes  from  Asia  overran  Europe- 
and  still  others  crossed  the  Alps  and  advanced  to  Rome 
The  spread  of  man  has  often  been  a  part  of  warfare  and  con- 
quest. This  is  illustrated  by  the  Roman  Empire  which,  bj 
conquest,  caused  the  diffusion  of  Romans  and  Roman  civili- 
zation, not  only  along  the  Mediterranean  shores,  but  through- 
out western  Europe,  even  as  far  as  the  British  Isles. 

The  discovery  of  new  lands,  especially  in  the  New  World, 
has  had  a  great  influence  on  the  spread  of  man.  By  the  time 
of  Columbus  there  had  been  such  advance  in  knowledge  of 
sailing,  including  the  coming  into  use  of  the  compass,  that 
even  the  ocean  could  be  crossed  at  will.  The  much  higher 
civilization  of  Europeans  enabled  them  to  displace  the  savage 
occupants,  not  only  of  America,  but  of  Australia  and  the 
more  attractive  parts  of  Africa.  Commerce  is  at  present 
aiding  in  the  general  spread  of  man. 

Summary.  —  The  spread  of  primitive  man  was  influenced  by  the 
same  laws  and  barriers  that  affect  animals  ;  but  man^s   superior 


382  NEW  PHYSICAL   GEOGRAPHY. 

inteUigeiice,  and  especially  the  use  of  boats,  clothing,  and  shelter,  has 
made  it  possible  for  him  to  spread  much  farther.  Man's  spread  has 
been  in  part  slow  migration,  in  part  rapid  movement  in  large  num- 
bers, often  as  a  part  of  ivarfare  and  conquest.  The  discovery  ofneio 
lands,  occupied  by  savages  whom  he  could  displace,  has  greatly  helped 
m  man^s  spread ;  and  commerce  is  now  aiding  it  further. 

253.  Races  of  Mankind.  —  Although  there  are  decided 
differences  among  men,  all  are  believed  to  have  come  from 
the  same  stock.  Through  the  influence  of  climate,  and  other 
surrounding  conditions,  they  have  become  varied  in  color, 
form,  and  habits.  On  account  of  these  differences  it  is  cus- 
tomary to  divide  mankind  into  several  classes,  or  races. 
There  is  (1)  the  black,  or  negro  (^Ethiopiari)  race  ;  (2)  the 
yellow  (^Mongolian')  race;  (3)  the  red,  or  Indian  (^Americany 
race;  and  (^4: )  the  white  (^Caucasian)  race.  A  fifth  division, 
the  brown  (^Malay)  race  (Fig.  545),  is  often  recognized. 

Because  there  has  been  a  mixture  of  blood  wherever  they  have 
come  in  contact,  the  boundaries  between  these  races  are  not  dis- 
tinct (Fig.  544).  Moreover,  the  members  of  one  race  have  often 
migrated  into  the  territory  of  another.  Thus  the  Finns  and  Hun- 
garians, though  surrounded  by  Caucasians,  are  Mongolian  in  origin. 

The  red  men  were  originally  confined  to  the  American  continent, 
and  have  never  migrated  to  other  regions.  But  other  races  have 
spread  widely.  In  modern  times  the  Mongolians  have  spread  very 
little,  and  the  negroes  have  spread  mainly  through  the  influence 
of  white  men,  who  have  carried  them  as  slaves,  especially  to  the 
\ew  World.  The  white  race,  on  the  other  hand,  has  migrated 
.extensively,  taking  the  place  of  weaker  and  less  well-fitted  people. 
This  is  well  illustrated  in  America,  where  the  Indians  have  been 
slowly  driven  back  by  the  aggressive,  civilized  Caucasians. 

Summary.  —  Mankiiid  is  divided  into  four  main  races:  (1)  the 
black,  or  Ethio/nau;  (2)  the  yelloiv,  or  3fongolian;  (3)  the  red,  or 
American;  and  (4)  the  'white,  or  Caucasian.  Because  of  intermi.V' 
tare  and  migration,  the  boundaries  betweeji  these  races  are  by  no 
means  distinct.  'The  white  race  is  now  rapidly  extending  its  range 
and  influence,  and  is  taking  2>'^*'^s'e.s'i'/o?i  of  the  earth. 


Fig.  545. —  Races  oi'  iiuiiikiiid.  Ked,  or  Jiidiaii,  upper  left;  black,  or  Etliiopiaii, 
upper  right;  white,  or  Caucasiau,  middle;  yellow,  or  Mongoliau,  lower 
right;  brown,  or  Malay  (a  branch  of  the  yellow  race),  lower  left- 


CHARACtJSklSTiCS    OF    THE    kACES    OF    MANKlND.i 


■rmer 


Ethiopian. 


Africa,  south  of  Sa- 
hara ;  Madagascar  ; 
Australasia  (for  ex- 
ample, Philippine 
Negritos). 


Africa;  United  States; 
West   Indies  ;   Nic- 


aragua ; 
Brazil. 


Guian?. : 


Long,  narrow  head; 
projecting  jaws ; 
broad,  flat  nose ; 
thick  lips,  rolled 
outward ;  large, 
round,  black  eyes  ; 
deep  brown  color, 
rarely  black  ;  short, 
black,  woolly  hair ; 
scanty  beard;  height 
above  average. 


Unintellectual ;  un- 
progressive ;  no  sci- 
ence or  letters ;  few 
arts  beyond  agricul- 
ture and  simple 
weaving,  pottery 
making,  etc. ;  re- 
ligion very  crude, 
including  witch- 
craft, nature  wor- 
ship, and  human 
sacrifice. 


Africa 

Madagas- 
car 
America 
Austral- 
asia 

Total 


150,000,000 

8.000,000 
20,000,000 

2.000.000 


175,000,000 


Mongolian. 


Probably 
Tibet. 


highlands  ■  of 


China ;  Indo-China ; 
North  Asia  ;  Korea  ; 
Japan  ;  Malaysia  ; 
Turkestan;  Asia  Mi- 
nor ;  Russia  (Baltic) : 
Balkan  Peninsula ; 
Hungary. 


Broad,  round  head ; 
moderately  projecting 
jaws ;  small,  concave 
nose;  thin  lips;  small, 
oblique,  black  eyes ; 
color  yellowish,  pale, 
and  even  white  ;  long, 
coarse,  black  hair ; 
no  beard ;  height 
below  the  average. 


in- 


Sullen ;  sluggish 
dustrious  in  temper- 
ate zone,  elsewhere 
indolent ;  arts  and 
letters  moderately 
developed ;  science 
slightly;  their  culture 
not  of  modern  kind. 
In  religion  some  are 
pagans,  but  most  are 
Buddhists  and  Mo- 
hammedans. 


China, 

Jai)an  and 
Korea, 

Indo-China, 

Malavsia,2 

Eest"of 
Asia, 

Miscella- 
neous, 

Total, 


380,000,000 

55,000,000 
85,000,000 
80,000,000 

36,000,000 

4,000,000 


540,000,000 


Amkkican. 


New  World. 


Most  are  now  found 
in  Mexico,  Oe!itral 
America,  South 

America,     and    west- 
ern United  States. 


Head  both  long  and 
round  ;  slightly  pro- 
jecting, massive  jaws ; 
aquiline  nose ;  small, 
black  eyes;  coloi-  cop- 
perv,  shading  to  yel- 
lowish or  brown ;  hair 
long,  coarse,  black  ; 
scanty  beard ;  height 
variable. 


Stern  ;  moody  ;  not  emo- 
tional ;  vary  from 
saA-agery  to  barba- 
rism ;  slight  knowl- 
edge of  arts,  for 
example,  agriculture, 
I)ottery,  etc.  Highest 
had  rude  knowledge 
of  letters  and  some 
simple  science.  Ee- 
ligion  a  superstition, 
with  nature  worship 
and  human  sacrifice. 


Caucasian. 


North  Africa. 


All  of  Europe;  India; 
northern,  central,  and 
western  Asia;  America: 
South  Africa;  Austral- 
asia ;  New  Zealand ;  in 
fact,  over  almost  all  the 
world. 


Full  blood,         9,000,000 
Half-breeds,     12.270,000 

Total  22.170.000 

Most  in  Mexico  (8,705.- 

00(1):  Brazil,  4,200,000: 

250,000      in       United 

States. 


Two  types  :  (1)  fair  ;  head 
long ;  moderately  large, 
blue  or  gray  eyes  ;  long 
flixen,  brown,  or  red 
hair ;  height  above  the 
avei'age  ;  (2)  dark  ;  head 
long  in  south,  round  in 
north  ;  hu-ge  black  eyes; 
ha  r  wavv,  curly,  brown 
or  black.  In  both  types 
jaws  small,  nose  large, 
'straight,  or  aquiline. 


Fair  type  solid  and  even 
stolid  ;  dark  type  fiery 
and  fickle.  Both  active 
and  enterprising.  Sci- 
ence, letters,  and  art 
highly  developed.  Be- 
ligion  varies  from  belief 
in  one  God  to  belief  in 
several,  and  includes 
Christianity,  Judaism, 
M  ohammedanism,  Brah- 
manism. 


Europe, 

Asia. 

America, 

Africa, 

Australasia, 

Total 


355,000,000 

280,000.000 

115.000,000 

15,000.000 

5,000.000 

770,000,000 


»  Based  on  table  in  Mill's  International  Geography. 

2  The  brown  race  (Fig.  545),  often  recognized  as  a  fifth  division  of  the  human  v»<te 
\m  Muugolians. 


■■=  here  included  amon<j 


384 


NEW  PHYSICAL   GEOGRAPHY. 


INFLUENCE   OF   SURROUNDINGS. 

254.  Man  in  the  Arctic.  — Agriculture  is  impossible  in  the 
Arctic,  and  tiiere  is  too  little  ])lant  food  to  support  liumau 
life  (Fig.  486).  Under  such  unfavorable  conditions,  the 
inhabitants  of  the  North  must  look  to  animals  for  food  ;  and, 

as  these  are  most 
abundant  in  the 
sea,  the  shores  of 
the  Arctic  are  in- 
habited by  a  sparse 
population.  On 
the  tundras  of  Eu- 
rope and  Asia,  the 
reindeer  is  domesti- 
cated, making  it 
possible  for  more 
people  to  live  than 
otherwise  could. 
The  caribou  is  not 
used  by  the  Eskimos ;  but  Siberian  reindeer  have  recently 
been  introduced  into  Alaska. 

Life  in  the  Arctic  is  well  illustrated  by  the  Eskimos  (Figs.  524, 
525),  who  live  along  the  coast,  depending  for  food  chiefly  on  birds, 
seal,  walrus,  and  bear.  The  extent  to  which  these  interesting  peo- 
ple depend  on  animals  is  shown  by  the  following :  they  obtain 
from  them  most  of  their  food ;  skins  for  their  clothing  and  sum- 
mer tents,  or  tuples;  bone  for  their  spears;  and  bone  framework 
and  skins  for  their  boats,  or  kayaks.  Wood,  occasionally  drifted 
to  their  shores,  is  one  of  their  most  highly  prized  possessions. 

To  live  amid  such  surroimdings  reqnires  great  hardiness  and 
constant  effort;  and  death  by  starvation  is  not  uncommon.  The 
Eskimo  has  to  work  hard  in  order  to  obtain  the  barest  necessi- 
ties, and  there  are  no  luxuries.  How  difficult  his  life  must  be  is 
indicated  by  the  disasters  which  have  befallen  many  Arctic  ex- 
plorers.    Such  surroundings  oifer  little  opportunity  for  advance. 


Fig.  546.  —  Natives  near  the  timber  line  in  northern 
Asia.    Both  the  dog  and  reindeer  are  domesticated. 


MAN  AND  NATURE,  385 

Summary.  —  The  Arctic  is  sparsely  populated,  mainly  along  the 
coast  Inhere  there  is  most  animal  food;  hut  in  the  Old  World  the 
reindeer  is  domesticated,  increasing  man's  chance  of  living.  The  Es- 
kimo depends  on  animals  for  food  and  materials  for  shelter,  cloth- 
ing, and  boats.  Life  in  the  Arctic  is  so  hard  that  there  is  little  chance 
for  advance,  all  the  energies  being  needed  for  obtaining  the  barest 
necessities, 

255.  Man  in  the  Tropical  Zone.  — Conditions  in  the  tropical 
zone  are  quite  opposite  to  those  in  the  Arctic.  There  man 
is  surrounded  by  an  abundance  of  food,  both  plant  and 
animal,  and  he  requires  little  clothing  (Fig.  522)  or  shelter 
(Figs.  527,  529,  530).  All  his  needs  are  met  with  slight  effort, 
und  there  is  little  cause  for  work.  Moreover,  the  climate, 
especially  if  damp,  is  unfavorable  to  work.  Under  such  con- 
ditions man  resembles  animals  in  being  content  with  bare 
necessities.  Being  so  easily  satisfied,  he  cannot  advance 
far  in  civilization. 

It  is  for  these  reasons  that  some  of  the  most  uncivilized  peoples 
of  the  world  to-day  are  found  in  hot  climates.  The  Indians  of 
Central  and  South  America,  the  negroes  of  central  Africa,  tlie 
Australian  natives,  and  the  Negritos  of  the  Philippines  are 
examples.  Among  many  of  these  people,  as  among  animals,  the 
eating  of  one  another,  or  cannibalism,  is  still  practiced.  They 
live  in  the  most  primitive  way,  —  lazy,  unintelligent,  superstitious, 
human  animals.  Yet  they  talk,  they  think  a  little,  and  they  know 
the  use  of  simple  implements.  When  brought  under  the  influence 
of  civilization  they  advance,  showing  that  it  is  only  surrounding 
conditions  that  have  kept  them  so  low. 

Summary.  —  In  the  tropical  zone  the  ease  of  obtaining  food,  and 
the  small  amount  of  clothing  and  shelter  necessary,  call  for  little  ivorTc, 
to  which  the  hot,  damp  climate  is  unfavorable.  It  is  for  these  reasons 
that  the  least  civilized  races  are  found  in  the  tropical  zone. 

256.  Man  in  the  Temperate  Zone.  —  This  zone  has  been  the 
birthplace  of  civilization,  mainly  for  the  following  reasons  : 
(1)  while  there  is  an  abundance  of  food  in  summer,  there 

2c 


386  NEW  PHYSICAL    GEOGRAPHY. 

is  little  in  winter.  It  has,  therefore,  been  necessary  to  secure 
food  in  summer  and  store  it  for  winter  use.  This  requires 
energy,  intelligence,  and  foresight  ;  yet  the  amount  of  work 
necessary  is  not  great  enough  to  discourage  or  to  prevent  ad- 
vance. (2)  Both  clothing  and  shelter  are  needed,  and  to  pro- 
vide these  also  requires  intelligence,  ingenuity,  and  energy. 
(3)  The  lands  of  the  temperate  zone  are  irregular,  and  the 
climate  vai  led.  This  has  led  to  the  growth  of  different  crops\ 
in  different  sections  ;  and  the  people  of  one  section,  desiring 
the  products  of  another,  have  opened  communication  with 
them.  From  this  has  arisen  commerce,  leading  people  of  one 
region  to  learn  from  those  of  anotlier. 

To  meet  the  needs  of  winter,  the  people  of  the  temperate 
zone  have  developed  the  habit  of  cultivating  crops,  and  have  de- 
vised means  of  making  work  easier.  They  have  domesticated 
animals  for  food  and  as  aids  in  their  work ;  they  have  made  im- 
plements ;  have  learned  how  to  use  metals  ;  have  developed  the 
art  of  building;  have  discovered  the  use  of  fire;  in  fact,  in  sup- 
plying their  needs  they  have  learned  to  call  all  nature  to  their 
aid.  The  civilization  that  developed  in  the  north  temperate  zone 
has  now  spread  to  all  zones. 

Summary. —  T7ie  need  of  providing  food,  clothing,  and  shelter  for 
ivinter  has  caused  x^^ople  of  the  temperate  zone  to  advance;  and  the 
varied  products  of  different  sections  have  given  rise  to  commerce.  In 
this  advance  the  cidtication  of  crops,  the  lomestication  of  animals,  the 
art  of  building,  and  the  use  of  metcds  md  fire  have  been  learned. 
Thus  modern  cicilization  has  arisen. 

257.  Man  in  the  Desert.  —  Living  on  a  desert  resembles 
life  in  the  Arctic  in  the  fact  that  there  is  so  little  food  that 
laien  often  die  of  starvation.  But  the  nomads  of  the  desert 
(p.  89)  have  domestic  animals,  —  cattle,  horses,  and  camels 
especially,  —  which  hel[)  them  greatly.  Their  mode  of  life 
makes  these  wanderers  intelligent  and  brave,  otherwise  they 
could  not  live  amid  such  surroundings;  but  they  do  not 
hesitate  to  seize  from  others  the  goods  they  need 


MAN  AND  NATURE.  387 

Desert  conditions  are  so  unfavorable  that  people  more  civilized 
have  not  entered  to  crowd  the  nomads  out ;  and  the  desert  barrier 
prevents  the  inhabitants  from  learning  of  others.  For  this  reason, 
customs  of  the  time  of  Christ  are  to-day  preserved  among  the 
inhabitants  of  the  Old  World  deserts. 

On  oases  conditions  are  very  different,  for  there  agri- 
culture is  possible.  Large  oases,  such  as  the  valleys  of  the 
Euphrates  and  Nile,  have  been  cradles  of  ancient  civiliza- 
tion. Civilization  early  developed  in  such  situations  be- 
cause it  was  necessary  to  work  in  order  to  store  up  food  for 
the  season  when  crops  will  not  grow;  and  the  surrounding 
desert  served  to  protect  the  stores  of  food  from  invaders. 

Both  in  the  Euphrates  and  Nile  valleys,  and  in  other  oases  of 
the  Old  World,  there  developed  a  wonderful  ancient  civilization, 
which  spread  along  the  shores  of  the  Mediterranean.  This  an- 
cient culture  is  the  foundation  of  our  modern  civilization.  The 
oases  were  favorable  to  the  beginning,  and  the  Mediterranean  to 
the  spread  of  civilization  (p.  377) ;  but  the  desert  barrier  has  in- 
terfered with  the  introduction  of  the  modern  civilization  which 
has  developed  in  other  parts  of  the  temperate  zone.  Consequently, 
these  cradles  of  ancient  civilization  are  now  far  behind  the  world. 

The  most  advanced  of  the  American  Indians  were  those  that 
lived  in  similar  situations.  The  Pueblo  Indians  of  New  Mexico, 
the  Aztecs  of  Mexico,  and  the  Incas  of  South  America  lived  in 
positions  where  agriculture  was  possible,  and  where  deserts  or 
mountains  offered  partial  protection  from  invasion.  When  dis- 
covered, these  red  men  were  barbarians,  far  higher  than  the  other 
Indians,  who  were  savages. 

Summary. —  Because  of  lack  of  food  and  icater,  desert  conditions 
are  unfavorable,  and  the  inhabitants  are  scattered  and  nomadic, 
though  greatly  aided  by  their  domestic  animals.  The  desert  barrier 
prevents  them  from  learning  from  others,  and  hence  they  preserve 
many  ancient  customs.  The  oases,  however,  ivere  cradles  of  ancient 
civilization,  because  (1)  agrictdture  ivas  possible ;  (2)  it  was  necessary 
to  provide  food  for  the  unfavorable  seasons;  and  (3)  the  desert  pro- 
tected the  inhabitants  from  invasion. 


388  NEW  PHYSICAL   GEOGRAPHY. 

258.  Influence  of  Mountains. —  There  is  no  part  of  tlie 
world  where,  in  so  short  a  distance,  there  are  found  races  so 
different  as  those  on  the  north  and  south  sides  of  the  Hima- 
layas. These  mountains  have  served  as  great  walls  (p.  106), 
hindering  the  migration  of  man  as  well  as  of  animals ;  and  it 
was  partly  because  of  their  protection  that  the  people  of  India 
became  so  civilized  in  very  ancient  times.  Yet  even  these 
mountain  barriers  were  crossed,  although  with  great  diffi- 
culty. Much  the  same  is  true  of  the  Alps,  whose  protection 
helped  to  make  the  powerful  Roman  Empire  possible. 

When  their  country  is  invaded,  people  often  retreat  to 
mountains;  for  there  is  little  about  mountains  to  attract  in- 
vaders, and  entrance  is  difficult,  while  the  passes  and  valleys 
are  easily  defended.  For  these  reasons  the  Welsh  and  Scotch, 
who  occupied  the  more  mountainous  parts  of  Great  Britain, 
were  far  less  affected  by  the  inroads  of  invaders  than  the  in- 
habitants of  other  sections  of  the  island.  To  this  day  their 
ancient  language  is  spoken,  and  sermons  are  even  preached 
in  it.  In  the  Pyrenees  there  is  a  small  group  of  people, 
called  the  Basques,  who  still  retain  an  ancient  language  no 
longer  spoken  by  others.  In  the  single  small  country  of 
Switzerland  four  languages  are  now  spoken,  —  German, 
French,  Italian,  and  Rsetho-Romisch  dialect. 

Among  mountain  people  ancient  customs,  as  well  as  languages, 
are  preserved.  For  example,  homespun  is  still  used  in  the  moun- 
tains of  eastern  Kentucky;  and  peculiar,  old-style  costumes  are 
worn  by  Swiss  mountaineers  and  inhabitants  of  the  Black  Forest 
mountains  of  Germany.  Such  places,  like  deserts,  are  among  the 
last  to  be  reached  by  new  customs. 

Mountain  people  are  brave  and  hardy,  for  their  life  is  one  of 
hardship,  and  there  are  many  dangers.  The  open-air  life,  with 
plenty  of  space  and  freedom,  develops  a  love  of  freedom.  They 
desire  to  be  left  alone,  and  resist  attempts  at  conquest.  It  is  for 
such  reasons  that  little  Switzerland,  notwithstanding  many  efforts 
to  seize  it,  has  been  able  to  remain  independent. 


MAN  AND  NATURE.  389 

bummary.  —  Mountains  are  harriers,  protecting  people  from 
invasion;  they  are  places  of  retreat  before  invaders;  in  tJiem 
ancient  languages  and  customs  linger ;  they  develop)  a  brave,  hardy, 
freedom-loving  race. 

259.  Influence  of  Coast  Line.  —  Closed  seas  and  irregular 
coasts,  having  quiet  water,  encourage  fishing  and  commerce. 
It  is  along  such  coasts,  therefore,  that  navigation  has  devel- 
oped. The  Mediterranean  and  the  irregular  Grecian  coast 
illustrate  this;  also  the  irregular  Scandinavian  coast,  with 
its  many  narrow,  quiet  fiords  (p.  209).  Here  developed 
the  brave,  hardy  Norsemen,  who  ravaged  the  coast  of  west- 
ern Europe,  and  even  visited  America,  before  the  time  of 
Columbus. 

The  British  nation  has  become  "  mistress  of  the  seas " 
because  of  the  favorable  position  and  coast.  No  part  of  the 
British  Isles  is  far  from  the  sea;  there  are  innumerable  bays 
and  harbors;  and  many  of  the  inhabitants  have  engaged  in 
fishing.  The  separation  from  the  mainland  has  been  of 
the  highest  importance,  for  it  has  prevented  invasion  by 
land  and  has  made  commerce  by  water  necessary.  Further- 
more, these  small  islands  are  unable  to  supply  food  enough 
for  the  large  manufacturing  population  that  has  developed 
there.  To  bring  food,  and  to  carry  away  manufactured 
products,  calls  for  ships  ;  and  to  protect  these  and  the  coast 
from  attack,  demands  a  navy. 

Colonies  were  established  as  a  source  of  food  and  raw 
products  for  manufacture  ;  they  also  served  as  a  market  for 
manufactured  articles,  and  commerce  with  them  became 
great  and  mutually  beneficial.  As  a  result  of  these  facts,  and 
the  presence  of  coal  and  iron  for  manufacturing,  the  British 
nation  has  become  the  greatest  sea  power  in  the  world,  and 
has  come  into  possession  of  the  largest  amount  of  territory 
that  any  nation  has  ever  controlled. 

Summary.  —  Protected  seas,  like  the  Mediterranean,  and  irregular 
coasts^  like  those  of  Greece  and  Scandinavia,  encourage  the  develop- 


390 


KEW  PHYSICAL   GEOGRAPHY, 


ment  oj  navigation.  Tlie  British  nation  has  become  the  greatest  sea 
jyoiver,  and  the  x>ossessor  of  the  largest  amount  of  territory,  of  all 
nations,  as  a  result  of  its  island  condition,  its  irregular  coast,  and 
the  fact  that  it  needed  to  import  food  and  raw  products  for  manufac- 
ture, and,  being  on  an  island,  was  obliged  to  bring  them  by  water. 


260.  United  States.  —  The  situation  of  United  States  in 
the  temperate  zone,  witli  several  different  climates,  is  favor- 
able to  advaaice.  There  are 
great  natural  resources  of 
nearly  every  kind,  and  the 
wisdom  and  love  of  freedom 
of  our  ancestors  led  them  to 
establish  a  government  that 
has  encouraged  the  full  use 
of  these  resources.  The 
coast  line  is  favorable  to 
navigation,  and  the  Atlantic 
Ocean,  which  separates  us 
from  other  highly  civilized 
nations,  is  so  narrow  that 
communication  and  com- 
merce with  them  are  easily 
possible.  Yet  it  is  wide 
enough  to  protect  us  from 
attack  and  invasion. 

Early  settlements  were 
naturally  first  made  along  the  coast,  because  this  was  the  first 
place  reached.  Although  the  natives  were  finally  pushed 
aside,  for  a  while  aided  by  the  mountain  and  forest  barrier, 
they  held  back  the  westward  advance  of  the  pioneers. 
Thus  the  settlers  continued  to  live  along  the  coast ;  and  in 
1790,  when  the  West  was  a  vast  wilderness  crossed  only  by 
Indian  trails,  it  was  possible  to  travel  by  stage  from  Portland, 
Me.,  to  Virginia,  stopping  each  nisht  in  a  good-sized  village. 


1  **4i  Ko  settlers  except  Indians  who  roamed  about. 

YVA  Scattered  settlements,  such  as  forts,  pioneer  hoosefl  and  small  villagM. 
^'  ■  ■  i  Fairly  well  settled. 

p^^  Most  densely  settled  portion.    More  than  90  people  living  on 
BYerj  square  mile. 

Fig.  547. — Distribution   of   white   men 
.  in  United  States,  1790. 


MAN  AND  NATURE.  391 

The  Spanish  and  French  settlements  were  far  more  scat- 
tered, for  the  Spanish  had  two  coasts  along  which  to  travel, 
and  the  French  the  great  interior  waterways.  Therefore, 
when  the  French  and  Indian  war  came,  the  English,  being 
closer  together  and  able  to  unite,  had  a  great  advantage. 
The  success  of  the  Revolution  was  also  in  large  part  due 
to  the  fact  tliat  the  Colonists  were  centered  along  the  coast. 

The  mountains  were  finally  crossed  along  the  water  gaps, 
through  Cumberland  Gap  to  Tennessee  and  Kentucky,  and 
along  the  Mohawk  Gap  to  the  Great  Lakes.  When  the 
way  to  the  interior  was  wejl  opened,  migration  was  rapid, 
because  the  soil  was  good,  the  climate  favorable,  the  surface 
clear  of  forest,  and  the  land  free  to  all.  Soon  the  central 
plains  developed  into  a  great  agricultural,  mining,  and 
manufacturing  section.  The  water  gaps  and  waterways  are 
still  the  leading  routes  to  i:his  interior. 

West  of  the  prairies  was  another  great  barrier,  in  the  form 
of  arid  plains  and  plateaus,  extensive  deserts,  and  lofty 
mountain  ranges.  How  great  a  barrier  this  was  is  seen  from 
the  fact  that,  when  gold  was  discovered  in  California,  large 
numbers  preferred  to  travel  entirely  around  South  America 
rather  than  undergo  the  danger  and  hardship  of  a  wagon 
trip  across  the  continent.  Now  several  lines  of  railway 
cross  the  mountains;  there  are  mining  cities  in  the  mountain 
valleys;  and  irrigated  farms  dot  even  the  desert.  Man  has 
so  overcome  these  barriers  that  the  continent  is  crossed  in  a 
few  days  with  all  the  comforts  of  modern  railway  travel. 

Our  country  has  developed  wonderfully,  and  in  a  century 
has  changed  from  a  weak  nation,  struggling  for  existence,  to 
one  of  the  great  world  powers.  This  growth  is  not  the  result 
of  a  mere  accident ;  nor  is  it  due  to  a  single  cause.  The 
invigorating  climate  encourages  work,  and  in  fact  requires 
it ;  and  intelligent  labor  secures  great  reward.  In  a  new 
country  there  are  wide  opportunities  for  those  who  work 
hard,  and  this  fact  has  helped  make  the  American  people 


892  NEW  PHYSICAL   GEOGRAPHY, 

energetic.  Mineral,  farm,  and  forest  products  may  be  ob- 
tained in  great  variety;  and  physiographic  conditions,  as 
well  as  the  wise  government  under  which  we  live,  are  favor- 
able to  their  development.  It  is  no  wonder  that  the  United 
States  has  advanced  so  rapidly  ;  and  the  present  century 
should  see  still  more  wonderful  advancement. 

Summary.  —  TJie  climate,  resources,  government,  and  coast  line 
of  the  United  States  are  favorable  to  2^^^ogress.  Hie  early  settle- 
ments along  the  coast,  and  the  interference  ivith  westward  spread, 
caused  by  the  Indians  and  mountain  barrier,  helped  make  the 
English  successful  in  ivar  ivith  Frtince,  and  the  colonists  in  the 
Mevoliction  against  the  mother  country.  The  mountaiyi  barrier  was 
first  crossed  along  the  water  gaps,  and  the  fertile,  open  prairie  tvas 
then  quickly  developed  ;  but  the  great  western  barrier  of  desert  and 
mountain  held  back  further  j^rogress  until  after  the  discovery  of  gold 
in  California.  Our  rajnd  development  has  depended  on  the  energetic 
people,  wise  government,  and  vast  resources;  ajid  since  the  foun^ 
dation  is  solid,  our  prosperity  promises  to  continue. 

Topical  Outline  and  Review  Questions. 

Topical  Outline.  —  243.  Early  Man.  —  Origin  by  evolution ;  resem- 
blance to  animals  ;  difference  from  animals;  early  stages  of  savagery. 

244.  Dependence  of  Man  on  Nature.  —  Dependence  of  all  mankind; 
further  dependence  of  civilized  man;  use  of  nature  by  civilized  man. 

245.  Food  Supply.  —  Basis  of  invention;  primitive  implements;  present 
use;  parts  of  plants  eaten;  instances;  reasons  for  cultivation;  impor- 
tance of  domestication  ;  farming  at  present;  dependence  on  farmer. 

246.  Clothing.  — •  Need  of  clothing  ;  materials  used ;  use  of  skins  ; 
vegetable  products  ;  animal  products ;  reason  for  importance. 

247.  Shelter. —  (a)  Primitive  shelters:  Eskimos;  Indians  ;  nomads  ; 
sod  houses ;  tropical  shelter ;  caves,  (b)  Building  materials  :  first  use  ; 
wood;  stone;  mortar;  sun-dried  brick;  baked  brick,  (c)  Fire:  need 
of  it ;  first  importance  ;  later  uses  ;  result  of  these  uses. 

248.  Selection  of  Homes.  —  Two  objects  in  selecting  sites ;  condition  of 
civilized  man  ;  instances  of  sites  selected  for  protection. 

249.  Location  and  Growth  of  Cities.  —  (a)  Primitive  man  :  reasons 
for  communities :  savages  ;  advantages  of  villages.  (&)  Government : 
village   chief ;     exTeusion   of    power  5    origin   of   modern   government. 


MAN    AND    NATURE.  S93 

(c)  European  towns:  castles;  gathering  of  people  about  them;  present 
condition,  (d)  Modern  cities:  capitals;  industries  in  large  capitals; 
cities  at  junction  of  trade  routes ;  on  rivers ;  lake  ports  ;  seaports ;  sea- 
ports at  mouths  of  rivers ;  effect  of  water  power;  of  mining. 

250.  Development  of  Commerce.  —  (a)  Exchange  :  desires  of  primitive 
people ;  methods  of  gratifying  them ;  early  commerce,  (b)  Greeks ; 
favorable  location ;  colonies  ;  extension  beyond  Mediterranean,  (c)  Dis- 
covery of  new  lands  :  reason  for  exploration  ;  results,  (d)  Eif ects  of  com- 
merce :  exchange;  need  of  money;  use  of  gold;  spread  of  civilization; 
'■iarly  writing  ;  alphabet ;  electricity. 

251.  Influence  of  Man  on  Nature. — Life;  forest  removal,  —  effect  on 
rivers,  on  soil ;  changes  in  stream  courses ;  irrigation  ;  lakes ;  work  along 
Reacoast;  borings;  mines;  quarrying;  tunnels;  roads;  plowing;  inde- 
pendence of  man ;  use  of  surroundings. 

252.  The  Spread  of  Man.  —  Resemblance  to  animals  ;  superior  intelli- 
gence ;  use  of  boats  ;  of  clothing  and  shelter ;  slow  spread  ;  rapid  spread  ; 
conquest;  discovery  of  new  lands;  aid  of  commerce. 

253.  Races  of  Mankind.  —  Origin  of  differences ;  the  races  ;  boundaries ; 
spread  of  the  red  race  ;  the  black  race ;  the  yellow  race ;  the  white  race. 

254.  Man  in  the  Arctic.  —  Plant  food;  animal  food  in  sea;  reindeer; 
Eskimos, — food,  dependence  on  animals,  wood,  effect  of  surroundings. 

255.  Man  in  the  Tropical  Zone.  —  Food  ;  ease  of  meeting  needs  ;  effect 
of  climate  on  civilization  ;  instances  of  uncivilized  people ;  their  condi- 
tion ;  possibility  of  advance. 

256.  Man  in  the  Temperate  Zone.  —  (a)  Reasons  for  civilization : 
abundant  food ;  need  of  storing  food  for  winter ;  need  of  clothing  and 
shelter;  varied  climate  and  land  form.  (&)  Nature  of  advance:  culti- 
vation of  crops;  domestication  of  animals;  use  of  implements;  of 
metals  ;  art  of  building  ;  use  of  fire. 

257.  Man  in  the  Desert. —  (a)  The  desert  itself:  comparison  with 
Arctic ;  domestic  animals ;  nomadic  characteristics ;  effect  of  desert 
barrier,  (b)  On  oases :  agriculture ;  cradles  of  civilization ;  reasons 
for  development  of  civilization,  (c)  Euphrates  and  Nile  :  early  civili- 
zation; its  spread;  present  condition,     (d)  American  Indians. 

258.  Influence  of  Mountains.  —  (a)  Barriers ;  races  on  two  sides  of 
Himalayg-s ;  protection  to  India;  Alps,  (b)  Retreats:  reasons;  Welsh 
and  Scotch ;  Basques;  Switzerland;  ancient  customs.  (c)  Mountain 
people  :  character  ;  love  of  freedom  ;  Switzerland. 

259.  Influence  of  Coast  Line.  —  (a)  Closed  seas :  Mediterranean. 
(&)  Irregular  coasts  :  Greece ;  Scandinavia,  (c)  British  nation  :  near- 
ness to  sea ;  irregular  coast ;  fishing  ;  island  condition ;  food  supply  ; 
colonies ;  commerce  ;  coal  and  iron  ;  great  importance. 


394  NEW  PHYSICAL   GEOGRAPHY. 

260.  United  States.  —  (a)  Favorable  conditions:  climate;  resources; 
government;  coast  line;  ocean,  (b)  Mountain  barrier:  first  settlements; 
natives ;  barrier  to  westward  movement ;  condition  in  1790 ;  Spanish ; 
French;  French  and  Indian  war;  Revolution,  (c)  Interior:  crossing 
barrier ;  development  of  interior ;  present  routes  to  interior,  (d)  Western 
barrier:  nature;  difficulty  of  crossing;  present  condition,  (e)  Growth 
of  country  :  climate ;  energetic  people ;  resources  ;  government ;  future. 

Review  Questions.  —  243.  What  is  believed  to  be  the  origin  of 
man?    What  was  his  early  state? 

244.  Upon  what  conditions  are  all  men  dependent?  In  what  other 
ways  are  civilized  men  dependent  on  nature  ? 

245.  What  simple  implements  were  early  used?  Why?  Why  were 
plants  cultivated?  What  parts  are  used?  Give  examples.  Of  what  im- 
portance is  domestication  ?     Of  what  present  importance  is  agriculture  ? 

246.  What  materials  are  used  for  clothing?  Why  are  the  production 
and  manufacture  of  materials  for  clothing  so  important? 

247.  What  primitive  means  are  employed  for  securing  shelter?  How 
has  the  use  of  wood  developed?    Stone?     Clay?     Of  what  use  is  fire? 

248.  What  considerations  have  led  to  the  selection  of  sites  for  homes? 
What  influences  civilized  man  ?     Give  illustrations  of  protected  sites. 

249.  Why  do  men  gather  in  centers?  Illustrate.  What  influence 
has  this  on  government?  What  was  the  condition  in  Europe ?  What 
great  European  cities  are  capitals?  What  else  accounts  for  their 
growth?  What  situations  especially  favor  the  growth  of  cities?  Give 
instances.     In  what  several  connections  is  London  mentioned? 

250.  What  is  the  nature  of  commerce  among  primitive  peoples?  How 
was  early  commerce  carried  on  ?  What  was  the  nature  of  ancient  coni' 
merce  between  Asia  and  Europe  ?  What  influence  had  the  Mediterra- 
nean ?  What  effect  had  the  Mohammedans?  On  what  does  the  use  of 
money  depend?     Why  is  gold  used?     State  other  effects  of  commerce. 

251.  State  some  of  the  ways  in  which  man  influences  nature  :  (a)  life ; 
(b)  rivers ;  (c)  seacoast ;   (d)  the  land. 

252.  Compare  and  contrast  man's  spread  with  that  of  animals.  In 
what  ways  has  his  spread  been  accomplished?     Give  illustrations. 

2.53.  What  is  the  cause  of  differences  among  men?  Name  the  four 
races.  Where  is  each  mainly  found  (Fig.  .544)  ?  Why  are  the  bound- 
aries not  sharp  ?     What  about  the  spread  of  the  different  "races  ? 

2.54.  What  are  the  sources  of  food  for  the  inhabitants  of  the  Arctic  ? 
How  do  the  Eskimos  liv^e  ?     Why  may  they  not  advance  ? 

255,  What  conditions  in  the  tropical  zone  are  unfavorable  to  civiliza- 
tion ?     What  is  the  condition  of  the  inhabitants  ?     Can  they  be  civilized  "^ 

256.  What  three  conditions  bave  favored  ^-dvance  to  civilization  in 


MAN  AND  NATURE.  395 

the  temperate  zone?     How  have  they  aided?     In  what  ways  has  man 
learned  to  call  nature  to  his  service  ? 

257.  What  is  the  condition  of  man  in  the  desert  ?  Why  are  primitive 
customs  preserved?  Why  were  oases  favorable  to  the  development  of 
early  civilization?  Of  what  importance  was  this  in  the  Old  World? 
What  was  the  condition  in  the  New  World? 

258.  What  are  the  effects  of  mountains  as  barriers?  Why  are  they 
places  of  retreat?  Give  illustrations  of  the  influence  of  this  on  language. 
On  customs.     What  effect  have  mountains  on  character  ? 

259.  Give  instances  of  the  influence  of  closed  seas  and  irregular 
coasts.     What  facts  account  for  the  importance  of  the  British  nation? 

260.  What  conditions  are  favorable  to  the  advance  of  the  United 
States  ?  What  were  the  nature  and  effects  of  the  barrier  west  of  the 
coast?  Where  was  this  barrier  crossed ?  What  was  the  result?  What 
barrier  was  found  farther  west  ?  How  has  it  been  overcome  ?  Upon 
what  has  our  progress  as  a  nation  depended  ? 

Reference  Books. —  Shaler,  Nature  and  Man  in  America,  Scribner's, 
Sons,  New  York,  1891,  $1.50;  Peschel,  Races  of  Man,  Appleton  &  Co., 
New  York,  1876,  $2.25 ;  Lubbock,  Origin  of  Civilization,  Appleton  &  Co., 
New  York,  1895,  $5.00;  Keane,  Ethnology,  2  vols.,  Macmillan  Co.,  New 
York,  1896,  $2.60;  Man,  Past  and  Present,  Macmillan  Co.,  New  York, 
1899,  $3.00;  Brintox,  Races  and  Peoples,  McKay,  Philadelphia,  1890, 
$1.50;  Ripley,  Races  of  Europe,  2  vols.,  Appleton  &  Co.,  New  York, 
1899,  $6.00;  Ratzel,  The  History  of  Mankind,  3  vols.,  Macmillan  Co., 
New  York,  1896-99,  $4.00  a  volume ;  Gibbins,  History  of  Commerce  in 
Europe,  Macmillan  Co.,  New  York,  1891,  $0.90 ;  Guyot,  The  Earth  and 
Man,  Scribner's  Sons,  New  York,  1893,  $1.75;  Marsh,  The  Earth  as 
Modified  by  Human  Action,  Scribner's  Sons,  New  York,  1885,  $3.50; 
Mackinder,  Britain  and  the  British  Seas,  Appleton  &  Co.,  New  York, 
1902,  $2.00. 


APPENDIXES. 

APPENDIX    A.     REVOLUTION   OF   THE   EARTH. 

1.  Apparent  Movements  of  the  Sun.  —  In  addition  to  tlie  daily 
rising  and  setting  of  the  sun  there  is  a  slower  change  in  its  posi- 
tion which  can  be  detected  by  noting  the  point  of  sunrise  or  sun- 
set for  a  week  or  two.  In  the  north  temperate  zone,  the  sun  rises 
exactly  in  the  east  and  sets  due  west  on  March  21  and  Septem- 
ber 23.  From  March  to  September  sunrise  and  sunset  are  north  of 
true  east  and  west,  and  the  days  are  longer  than  the  nights.  But 
from  September  to  March  the  sun  rises  and  sets  south  of  due  east 
and  west,  and  the  nights  are  then  longer  than  the  days.  The 
midday  sun  also  changes  in  position.  It  is  higher  in  summer 
than  in  winter,  but  is  always  in  the  southern  half  of  the  heavens. 
In  the  southern  hemisphere  the  same  changes  occur  in  the  opposite 
season  ;  but  there  the  midday  sun  is  always  in  the  northern  half 
of  the  heavens. 

2.  Experiment  to  Illustrate  Revolution.  —  One  or  two  simple 
experiments  will  aid  in  a  better  understanding  of  the  way  in 
which  revolution  (p.  5)  causes  these  apparent  movements  of  the 
sun.  Place  two  balls  in  a  tub  of  water  (Fig.  548),  one  in  the 
center  to  represent  the  sun,  the  other  off  to  one  side  to  represent 
the  earth.  The  water  surface  represents  the  plane  of  the  ecliptic, 
or  the  plane  in  which  the  earth  moves  in  its  revolution  around 
the  sun.  If  the  earth  ball  is  moved  around  the  central  ball,  its 
path  will  represent  the  orbit  of  the  earth  in  its  revolution. 

A  needle  inserted  in  the  earth  ball  represents  the  position  of 
the  earth's  axis.  When  the  ball  is  so  placed  that  the  needle  pro- 
jects straight  up  into  the  air,  the  axis  of  the  ball  is  perpendicular 
to  the  water  surface ;  if  the  axis  of  the  earth  were  in  a  similar 
position,  it  would  be  perpendicular  to  the  plane  of  the  ecliptic. 
Now  turn  the  earth  ball  until  the  needle  is  inclined  as  in  Figure 

397 


398 


NEW  PHYSICAL   GEOGRAPHY. 


548,  which  is  the  same  angle  as  that  at  which  the  earth's  axis  is 
inclined.  The  earth  is  inclined  66h°  to  the  plane  of  the  ecliptic, 
or  23 ^°  to  a  perpendicular  from  that  plane. 

Float  the  earth  ball  around  the  central  ball,  always  keeping  the 
needle  axis  inclined  at .  the  same  angle,  and  you  will  see  quite 
clearly  in  what  position  the  earth  moves  around  the  sun. 

Position  1  (Fig.  548),  with  the  needle  pointing  toivard  the  cen- 
tral ball,  may  represent  the  earth's  position  in  summer  when  the 

North  Pole  points 
toward  the  sun.  In 
the  ball  on  the  op- 
posite side  of  the 
tub  (3),  the  needle 
is  inclined  away 
from  the  sun  ball, 
as  the  North  Pole  is 
in  winter;  but  the 
other  end 
needle,  or, 
may  call 
South  Pole,  is  then 
inclined  toward  the 
sun  ball.  Halfway 
between  these  sum- 
mer and  winter  posi- 
tions (2  and  4)  the  axis  is  inclined  neither  toward  nor  away  from 
the  sun.     These  points  represent  spring  and  autumn. 

3.  Rotation  and  Revolution.  —  The  manner  in  which  revolution 
causes  the  sun's  position  in  the  heavens  to  change  may  be  under- 
stood by  another  simple  experiment.  Let  a  globe  or  ball  repre- 
sent the  earth,  and  a  lamp  or  candle  the  sun.  Carry  the  globe 
in  a  circular  path  around  the  light,  being  careful  to  always  keep 
the  axis  inclined  at  the  same  angle. 

When  the  position  is  that  of  summer,  the  full  rays  of  the  lamp 
illuminate  the  northern  half  of  the  globe  and  reach  beyond  the 
l)ole.  So  in  the  case  of  the  earth,  when  it  has  reached  the  summer 
position  in  its  orbit,  the  sun's  rays  reach  beyond  the  North  Pole, 
and  illuminate  all  the  space  within  the  Arctic  Circle  (Fig.  549). 


of 

the 

as 

we 

it. 

the 

Fig.  548.  —  To  illustrate  revolution  of  the  earth. 


REVOLUTION, 


399 


Fig.  549.  —  Position  of  the  earth  June  21. 


This  circle  is  located  23^°  from  the  pole  because  the  sun's  rays  of 
midsummer  (June  21)  reach  that  distance  beyond  the  North 
Pole.  They  reach  that  far  because  this  is  tlie  amount  that  the 
earth's  axis  is  inclined. 

Now  rotate  the  globe,  and 
you  will  see  that  all  points 
within  23J°  of  the  pole  are 
lighted  throughout  the  en- 
tire rotation.  The  same  is 
also  true  of  the  earth.  This 
makes  it  clear  why,  on  the 
longest  day,  June  21,  every 
point  within  the  Arctic 
Circle  has  sunlight  for  the  full  24  hours  (Fig.  550). 

Still  holding  the  globe  in  this  position,  observe  the  conditions 
at  the  opposite  end  of  the  axis,  or  the  South  Pole.  Even  when 
the  globe  is  rotated,  no  light  reaches  that  portion.  This  is  also 
true  of  the  earth  in  summer,  for  then  the  midday  sun  just  barely 
appears  on  the  Antarctic  Circle,  23i°  from  the  South  Pole.     All 

within  that  circle  is 
dark,  even  at  mid- 
day. 

Moving  the  globe 
to  the  opposite,  or 
winter,  position  (3, 
Fig.  548),  with  the 
North  Pole  inclined 
away  from  the  lamp, 
conditions  are  re- 
versed. All  is  dark- 
ness within  the 
Arctic  Circle,  while 
all  within  the  Ant- 
arctic Circle  is 
bathed       in      light 


Fig.  550.  —  The  sun  at  midnight  in  the  Arctic  in  sum- 
mer when  the  region  within  the  Arctic  circle  is 
lighted  during  the  entire  rotation. 


(Fig.  551).  This  is  the  earth's  condition  in  winter.  Thus,  each 
year  as  the  earth  revolves,  there  is  a  season  of  darkness  and  one 
of  light  around  each  pole. 


400 


NEW  PHYSICAL   GEOGRAPHY, 


Fig.  551.  —  Position  of  the  earth  December  21. 


If  the  globe  is  now  placed  in  the  position  of  spring  oi  autumn 
(2  and  4,  Fig.  548),  the  light  will  exactly  reach  each  pole.     The 

half  of  the  polar  region 
that  faces  the  lamp  is 
lighted,  the  half  away 
from  it  is  in  darkness ; 
but  by  rotating  the  globe 
the  dark  side  is  turned 
toward  the  light.  When 
the  earth  reaches  a  cor- 
responding position  in 
its  orbit,  it  is  divided 
into  a  dark  and  a  light  half  by  a  plane  passing  from  pole  to 
pole  (Fig.  552).  At  these  times,  the  equinoxes  (equal  nights),  all 
over  the  earth  day  and  niglit  are  each  12  hours  long.  One  period  is 
called  -yeniaZ  (spring)  equinox,  the  other  autumnal  (autumn)  equino?:. 
During  the  equinoxes,  when  the  sunlight  just  reaches  each  pole, 
the  midday  sun  is  directly  above  the  equator,  A-fter  December 
21,  in  all  parts  of  the  earth,  the  sun  appears  to  be  slowly  moving 
northward,  and  the  sunlight  slowly  creeps  over  the  curvature  of 
the  earth  into  the  Arctic.  After  the  earth  has  passed  its  summer 
position,  the  sun  seems,  from 


all  points  on  the  globe,  to 
be  slowly  moving  south- 
ward, and  the  sunlight  is 
gradually  withdrawn  from 
the  Arctic. 

If  the  earth's  axis  were 
perpendicular  to  the  plane 
of  the  ecliptic,  there  would 
be  no  such  changes;  but, 
since  it  is  inclined,  revolu- 
tion turns  one  hemisphere  toward  the  sun  for  a  time,  then  away 
from  it.  These  annual  changes  recur  so  regularly  that,  in  all  the 
time  of  human  history,  there  has  been  no  noticeable  change. 

Suggestions.  —  (1)  Study  Sections  2  and  3  at  the  same  time  that 
you  are  yourself  performing  the  experiments  described.  (2)  Make 
careful  observations  of  the  change  in.  the  sun  from  day  to  day.     On  a 


Fig.  552.— Position  of  the  earth  Septembt  r  23. 


REVOLUTION. 


401 


Fig.  553.  —  To  illustrate  the  revolution  of  the  earth  around  the  sun. 


platform,  or  table,  placed  where  the  sun  reaches  it  from  morning  till 
night,  draw  intersecting  north-south  (p.  419)  and  east-west  lines.  Where 
they  cross  drive  a  long  knitting  needle  into  the  table.  Once  a  week  at 
noon  mark  on  the  north-south  line  the  point  to  which  the  needle  shadow 
reaches.  Also  mark  the  point  reached  by  the  shadow  just  after  sunrise 
or  just  before  sunset.  What  movements  of  the  sun  cause  these  changes? 
Observe  also  the  exact  place  where  the  sun  sets  each  week.  (3)  In  what 
direction  does. your  shadow  point  at  noon?  In  what  direction  would  it 
point  in  South  Africa?  At  each  tropic,  in  the  middle  of  March,  June, 
September,  and  January?  At  the  equator?  What  is  the  direction  of  a 
shadow  at  noon  in  summer  in  the  Arctic?  At  midnight?  Are  .«"ch 
shadows  longer  or  shorter  than  in  the  temperate  zone? 
2d 


APPENDIX    B.     LATITUDE   AND    LONGITUDE. 

1.  Latitude.  —  The  most  convenient  method  of  locating  points 
on  the  spherical  earth  is  by  imaginary  circles  extending  in  oppo- 
site directions.  Any  point  can  then  be  definitely  located  by  the 
intersection  of  such  circles.  These  are  called  circles  of  latitude 
and  longitude^  names  given  when  the  extent  of  the  world  was  not 
known,  and  one  direction  (longitude)  was  supposed  to  be  the  long 
direction,  the  other  (latitude)  the  broad  direction. 

For  measurement  of  latitude  imaginary  circles  are  extended 
in  an  east-west  direction.  The  largest  circle  (about  25,000  miles), 
the  equator,  extends  around  the  earth  midway  between  the  poles. 
Other  circles  parallel  to  this,  and  called  parallels  of  latitude,  are 
located  at  intervals  between  the  equator  and  either  pole.  As  their 
distance  from  the  equator  increases,  these  circles  diminish  in 
diameter  (Fig.  554)  until,  at  the  poles,  a  circle  of  latitude  is 
reduced  to  a  point. 

For  convenience  in  use  the  parallels  are  numbered.  From  the 
equator  to  the  north  pole  there  are  90  parallels,  numbered  as 
degrees  (indicated  by  the  sign  °) ;  there  are  also  90  from  the  equa- 
tor to  the  south  pole.  The  equator  is  called  0°  latitude ;  the 
north  pole,  90°  north  latitude  (abbreviated  N.  Lat.);  the  south 
pole,  90°  south  latitude  (S.  Lat.).  The  Tropic  of  Cancer  is 
23i°  N.  Lat. ;  the  Arctic  Circle,  m^°  N.  Lat. ;  the  Tropic  of 
Capricorn,  23-1-°  S.  Lat. ;  the  Antarctic  Circle,  &Q^°  S.  Lat. 
Which  parallel  of  latitude  is  nearest  your  home  ? 

Since  there  are  180°  from  pole  to  pole  there  are  twice  that 
number,  or  360°,  in  a  complete  circle  extending  around  the  earth 
across  the  poles.  It  is  customary  to  divide  circles  into  360°. 
This  is  a  convenient  number  because  it  is  exactly  divisible  by 
so  many  numbers. 

The  length  of  a  degree  of  latitude,  that  is  the  distance  between 
two  circles,   varies   sli.<2;htly   because  the  earth  is  not  a  perfect 


LATITUDE  AND  LONGITUDE. 


403 


circle 

map. 

small 


tert*' 


sphere  (p.  3).  It  is  -g^-g-  of  the  circumference.  Divide  the  cir- 
cumference of  the  earth  (25,000  miles)  by  360.  At  the  equator  a 
degrees  is  about  68.7  miles,  at 
the  poles  about  69.4  miles. 

On  a  small  map  of  a  large 
area,  as  a  continent,  it  is  im- 
possible to  draw  every  paral- 
lel, for  the  lines  would  be 
too.  close  together.  Accord- 
ingly, every  fifth  or  tenth 
is  placed  on  such  a 
But  for  a  map  of  a 
section  (Fig.  78)  the 
degrees  are  too  far  apart,  and 
additional  circles  are  neces- 
sary. For  this  purpose  de- 
grees are  subdivided  into 
minutes  (indicated  '),  and 
minutes  into  seconds  (indi- 
cated " ).  There  are  60  sec- 
onds in  a  minute  of  latitude, 
and  60  minutes  in  a  degree.  What  is  the  latitude  of  your  town 
in  degrees,  minutes,  and  seconds  ? 

2.    Longitude.  —  Circles  of   latitude  serve  to  accurately  locate 

places  in  a  north-south  direc- 
tion ;  but  there  is  need  of  loca- 
tion in  an  east-west  direction 
also.  Circles  of  longitude 
serve  this  purpose.  These 
circles  all  start  from  the 
poles,  broadening  out  toward 
the  equator,  and  are  therefore 
not  parallel  (Fig.  554).  To 
them  the  name  meridian  is 
often  applied. 

At  the  equator  a  degree  of 
longitude  is  about  equal  to  a 
degree  of  latitude  (69  miles), 


^9/fude        fas 


Fig.  554. — To  show  how  the  meridians 
converge  at  the  pole.  Trace  the  0° 
meridian  to  the  opposite  side  of  the 
globe.    What  is  it  numbered  there  ? 


N.POLE 


BTeg.  555.  — The  earth  cut  in  halves  along 
the  Greenwich  meridian. 


404 


NEW  PHYSICAL   GEOGRAPHY. 


being  -^-^  of  the  earth's  circumference.  In  latitude  40°,  which  is 
a  much  smaller  circle  than  the  equator  (Fig.  554),  a  degree  of 
longitude,  gi^  of  that  circle  of  latitude,  is  only  about  53  miles. 
In  latitude  60°  a  degree  of  longitude  is  about  34.7  miles;  and  at 
the  poles,  where  all  the  meridians  come  together,  a  degree  of 
longitude  has  no  length. 

The  circles  of  longitude  are  numbered  as  degrees,  there  being 
360  degrees.  Since  there  is  no  such  natural  starting  point  as  the 
equator,  there  is  no  general  agreement  as  to  where  the  numbering 
of  meridians  shall  begin.  Most  nations,  however,  have  adopted 
as  the  0°,  or  pr^'me  meridian,  the  circle  that  passes  through  the 
Greenwich  Observatory,  just  outside  of  London.  From  this 
meridian  the  circles  are  numbered  up  to  180°  both  east  and  west. 
New  York  is  74°  W.  Long.  Jerusalem  is  35°  E.  Long.  What  is 
the  nearest  meridian  to  your  town  ? 

Degrees  of  longitude  are  divided  into  minutes  and  seconds, 

as  degrees  of  latitude 
are.  What  is  the  longi- 
tude of  your  home  in 
degrees,  minutes,  and 
seconds  ? 


7 
j  *'^ 

\^^^'-^  / 

-■i"»-''»\     "» 


BORMAY  i  CO.N.y 


Fig.  556.  —  Map  to  illustrate  standard  time  in 
United  States.  The  meridians  75°,  90°,  105°, 
and  120°,  extend  throujjh  the  middle  of  the 
four  time  belts.  The  irregular  boundaries 
are  due  to  the  fact  that  railways  have  chosen 
convenient  points  on  their  lines  to  make  the 
change. 


3.  Longitude  and  Time. 

—  Rotation  causes  the  sun 
to  appear  to  pass  com- 
pletely around  the  earth 
in  24  hours.  That  is,  it 
passes  over  360°  in  24 
hours;  and,  dividing  360 
by  24,  we  find  that  it  passes 
over  15°  in  an  hour.  From 
this  it  is  evident  that 
places  15°  apart  will  have 
just   one   hour's   difference 


in  time.  Formerly,  places 
in  United  States  kept  local  or  solar  time,  and  even  neighboring  cities 
might  have  a  different  time.  This  caused  so  much  inconvenience  that 
it  was  agreed  to  adopt  a  standard  time,  by  which  the  time  changes  one 
hour  for  every  15°  of  longitude.  Now  in  traveling  across  the  continent 
one  need  change  his  watch  only  three  times  (Fig.  556). 


LATITUDE  AND  LONGITUDE.  405 

If  longitude  may  be  used  to  determine  time,  it  is  evident  that  time 
may  be  used  to  determine  longitude.  Ships  crossing  the  ocean  are  able 
in  this  way  to  determine  their  position.  They  start  with  an  accurate 
clock,  or  chronometer,  set  to  Greenwich  time.  By  means  of  an  instru- 
ment, the  sextant,  an  officer  observes  the  sun  to  determine  the  local  noon, 
that  is,  the  time  when  the  sun  has  reached  its  highest  position.  Com- 
paring this  local  time  with  that  of  the  chronometer,  it  is  easy  to  tell  just 
how  many  minutes'  difference  there  is  between  Greenwich  time  and  that 
where  the  ship  is.  Knowing  that  one  hour's  difference  means  15°  of 
longitude,  the  longitude  of  the  ship  is  readily  determined. 

Suggestions. —  (1)  To  understand  the  need  of  circles  of  latitude 
and  longitude,  try  to  locate  New  York  City  without  these.  Do  the  same 
by  use  of  latitude  and  longitude.  (2)  By  tying  the  ends  of  strings  to- 
gether make  three  circles  so  that  one  will  fit  over  the  equator  of  a  globe, 
one  over  parallel  45°,  and  one  over  parallel  60°.  Make  three  other  circles 
for  meridians  and  place  them  on  the  globe,  one  over  0°  longitude,  one 
over  60°  west  longitude,  one  over  120°  west  longitude.  With  ink,  mark 
on  each  of  tlie  latitude  strings  the  place  where  two  of  the  meridians 
cross.  Take  the  strings  off,  and  measure  the  diameters  of  each.  How 
do  the  diameters  of  the  meridian  strings  compare  with  the  equator  string? 
How  do  the  three  latitude  strings  compare  in  diameter?  Measure  the 
distance  between  the  ink  marks  made  on  the  latitude  strings.  How  do 
these  distances  compare  ?  This  shows  how  the  length  of  degrees  of 
longitude  varies.  (3)  Get  a  local  surveyor  to  explain  and  illustrate  the 
method  of  determining  latitude  and  longitude.  (4)  Recall  your  previ- 
ous study  of  standard  time  (see  Second  Book  of  Ta^r  &  McMurry's 
Geographies,  p.  116).  If  the  earth  were  flat,  what  would  be  tne  effect  on 
time  ?  To  answer  this,  imagine  a  table  top  to  represent  the  earth.  Raise 
a  lighted  candle  up  to  the  edge  to  represent  the  rising  sun.  How  much 
of  the  table  do  the  rays  reach  at  once  ?  Is  any  more  of  the  table  reached 
as  the  candle  is  raised  higher  ?  Now,  to  represent  part  of  the  globular 
earth,  place  a  curved  object  on  the  table  top;  for  example,  a  large  sheet  of 
cardboard  or  blotting  paper,  resting  on  books  or  dishes.  How  much  of  this 
curved  surface  is  lighted  when  the  candle  is  raised  ?  Is  more  lighted  as 
the  candk  is  raisea  higheV? 


APPENDIX  C.  COMMON  MINERALS  AND  ROCKS. 

MINERALS 

This  appendix  should  be  studied  ivith  an  accompanying  use  of  mineral 
specimetis.  Each  mineral  should  be  carefully  examined  to  note  its  color,  hard- 
ness, cleavage,  luster,  aud  crystal  form.  The  text  may  be  referred  to,  but  each 
student  should  have  a  set  of  specimens  and  be  expected  to  find  the  features  visible. 

A  MINERAL  may  be  defined  as  a  single  element,  or  two  or  more 
elements  chemically  combined,  forming  a  part  of  the  earth's 
crust.  Some,  like  suli^hur,  consist  of  one  element;  but  most 
minerals  are  formed  by  a  combination  of  several.  For  example, 
quartz  is  made  of  silicon  and  oxygen;  one  of  the  feldspars  con- 
tains silicon,  oxygen,  aluminum,  and  potassium. 

There  are  about  2000  known  minerals,  of  which  only  one  or 
two  hundred  are  abundant,  while  less  than  a  dozen  are  common 
in  most  rocks.  The  more  important  of  the  rock-forming  min- 
erals are  described  below. 

1.  Common  Rock-forming  Minerals. —  Quartz.  —  This,  the  most 
common  of  minerals,  is  present  in  many  rocks  and  soils.  It  is 
made  of  silicon  and  oxygen,  forming  silica  (SiOg).  These  ele- 
ments are  so  firmly  united  that  quartz  does  not  decay ;  but  it  \9 
slightly  soluble  in  underground  water.  It  has  a  glassy  appear 
ance,  or  luster,  and  varies  in  color  from  clear  glassy  to  milk}? 
white,  blue,  rose-colored,  red,  and  variegated.  Agate,  opal, 
jasper,  and  chalcedony  are  varieties  of  silica.  It  is  so  hard  that 
it  will  scratch  glass,  but  is  brittle  and  easily  broken,  having  a 
shelly  or  conchoidal  fracture,  like  glass.  When  it  crystallizes  it 
takes  the  form  of  a  six-sided  (hexagonal)  prism  terminated  by  a 
six-sided  pyramid. 

The  Feldspars.  —  There  are  a  number  of  kinds  of  feldspar,  each 
formed  by  the  union  of  several  elements,  and  all  nearly  as  hard  as 
quartz.  Crystals  are  not  common.  Cleavage  planes,  extending 
through  feldspar,  cause  it  to  break  along  smooth  faces.     Unlik§ 

400 


MINERALS.  407 

quartz,  feldspar  is  not  soluble.  When  exposed  to  air  and  water, 
however,  it  decays,  becoming  dull  and  whitish ;  and,  if  exposed 
long  enough,  the  hard  mineral  crumbles  to  a  whitish  clay,  or 
kaolin.  Many  soils  contain  decayed  feldspar,  and  some  of  the 
best  pottery  clays  are  kaolin.  Thus,  though  insoluble  and  nearly 
as  hard  as  quartz,  its  decay  makes  feldspar  less  durable. 

Calcite  (calcium  carbonate),  like  quartz,  varies  greatly  in  color. 
It  often  has  a  perfect  crystal  outline ;  and  since  it  has  cleavage 
in  three  directions,  when  broken  it  is  apt  to  take  the  form  of  a 
rhomb.  It  has  a  pearly  luster.  Unlike  quartz  and  feldspar,  cal- 
cite is  so  soft  that  a  knife  readily  scratches  it.  Moreover,  it  is 
one  of  the  most  soluble  of  common  minerals ;  and  the  cleavage 
planes  afford  opportunity  for  water  to  enter  and  dissolve  the 
mineral.  For  these  reasons  a  calcite  rock  is  far  less  durable  than 
one  made  of  feldspar  and  quartz. 

The  mineral  dolomite  resembles  calcite ;  but  it  is  less  soluble,  and 
has  a  different  chemical  composition.  Calcite  contains  calcium, 
carbon,  and  oxygen,  and  is,  therefore,  carbonate  of  lime  (CaCOg) ; 
dolomite  has  magnesium  in  addition,  and  is,  therefore,  magnesian 
carbonate  of  lime  ( (CaMg)  CO3). 

The  Micas.  —  There  are  a  number  of  different  minerals  belong- 
ing to  this  group,  all  having  a  complex  chemical  composition. 
Some  are  black,  some  colored,  and  some  so  colorless  that  they  are 
used  in  stove  doors  as  "  isinglass."  Two  of  the  most  common 
forms  are  biotite  and  muscovite,  the  former  dark  colored,  the  latter 
light.  All  are  easily  scratched  with  a  knife,  and  all  have  so  re- 
markable a  cleavage  that  they  readily  split  into  thin  sheets.  Some 
micas  decay  readily  ;  but  others  so  resist  decay  that  they  occur  as 
shiny  flakes  in  soils  and  some  rocks,  such  as  sandstones  and  shales. 

Hornblende  is  a  black  mineral  of  complex  chemical  composition, 
common  in  some  granites  and  lavas.  It  is  hard,  has  a  bright 
luster,  is  often  crystalline,  and  has  well-defined  cleavage.  When 
exposed  to  air  and  water  it  decays,  one  of  the  products  being  an 
iron  compound  which  stains  the  rock.  Iron  is  one  of  the  elements 
in  this  mineral. 

Augite,  found  in  many  lavas,  resembles  hornblende  in  several 
respects,  and  in  small  grains  is  difficult  to  distinguish  from  it. 
Its  chemical  composition,  crystal  form,  and  the  angle  at  which 


408  NEW   PHYSICAL    GEOGRAPHY. 

the  cleavage  faces  meet  are  different,  and  the  color  is  dark  greei? 
instead  of  black.     Like  hornblende  it  decays  readily. 

Iron  Ores.  —  Small  quantities  of  iron  are  present  in  many  minerals 
and  rocks,  and  the  yellow  and  red  color  of  soils  is  due  to  iron  stain. 
Among  the  iron  minerals  are  several  which  are  of  value  as  ores. 

Magnetite,  a  compound  of  iron  and  oxygen  (FegO^),  is  black,  hard, 
heavy,  usually  crystalline,  and  has  a  metallic  luster.  A  magnet  will 
attract  the  grains.  Hematite  (FegOg),  another  oxide  of  iron,  is  red  and 
either  earthy,  crystalline,  or  in  smooth,  rounded  masses.  Like  other 
iron  ores  it  is  heavy.  The  red  coloring  of  soils  is  due  to  a  hematite 
stain.  Limonite  is  yellow,  and  common  iron  rust  and  the  yellow  color  of 
soils  are  due  to  this  mineral.  It  is  an  iron  oxide  with  water,  or  a  hydrous 
oxide  (2Fe203  SHgO).  It  is  easy  to  determine  an  ore  of  iron  by  scratch- 
ing it  on  a  piece  of  white  quartz,  or  of  broken  china.  Magnetite  gives  a 
black  streak,  hematite  red,  and  limonite  yellow. 

Siderite,  the  carbonate  of  iron  (FeCOg),  is  a  heavy  brownish  mineral, 
resembling  calcite  in  general  appearance.  Iron  pyrite,  or  pyrites,  the 
sulphide  of  iron  (FeSg),  is  not  useful  as  an  ore.  It  is  a  hard,  heavy, 
golden  yellow  mineral,  sometimes  mistaken  for  gold,  and  hence  called 
"fool's  gold."     It  often  occurs  in  perfect  cubical  crystals. 

Gypsum,  the  sulphate  of  lime,  occurs  in  small  grains  in  many 
rocks,  and  sometimes  in  beds.  It  is  so  soft  that  it  can  be  scratched 
with  the  finger  nail ;  and,  being  soluble,  is  often  present  in  ^'  hard  " 
water.  The  color  varies,  but  is  often  white.  Sometimes  it  is 
well  crystallized,  then  having  such  perfect  cleavage  that  it  splits 
into  thin  flakes ;  but,  unlike  mica,  the  flakes  are  not  elastic. 

Minerals  in  Rocks.  —  The  tables  (pp.  410-413)  show  that  the 
common  rocks  are  made  chiefly  of  the  minerals  described  above. 
Other  minerals,  while  abundant  in  some  localities,  are  relatively 
rare  in  the  rocks  of  the  earth ;  but  some  of  the  rarer  minerals, 
such  as  the  ores  of  gold,  silver,  copper,  etc.,  are  of  great  value  to 
man. 

ROCKS. 

2.  Classification  of  the  Common  Rocks.  —  Rocks  are  mixtures  of 
minerals,  and  are  not  usually  of  definite  chemical  composition. 
They  may  be  classified  in  three  great  groups :  — 

(1)  Sedimentary  rocks,  most  of  which  were  deposited  in  water ; 
(2)  Igneous  rocks,  which  were  once  molten ;  and  (3)  Metamorphic 


ROCKS.  409 

rocks,  which  have  been  altered  from  some  previous  state  by  heat, 
pressure,  and  water.  A  few  of  the  most  common  are  described 
below. 

3.  Sedimentary  Rocks.  —  Fragmental  or  Clastic  Rocks.  —  By  the 
disintegration  of  rocks,  fragments  of  all  sizes,  from  clay  to  bowl- 
ders, are  detached.  When  assorted  by  water  these  are  deposited 
in  layers  (p.  33),  the  pebbles  forming  gravel  beds,  the  sand,  sand 
beds,  and  clay,  clay  beds.  Rock  fragments  may  also  be  brought 
by  glaciers,  by  wind,  and  by  volcanic  explosions,  which  supply 
ash  and  pumice.  These  fragmental,  or  clastic,  materials  may  be 
cemented  into  solid  rock  by  the  deposit  of  mineral  substances 
carried  by  underground  water  (p.  39). 

Consolidated  gravel  beds,  called  coyiglomerates,  are  composed  of 
whatever  minerals  were  in  the  rocks  from  which  the  pebbles  are 
derived.  Consolidated  sand  beds,  or  sandstones,  usually  consist 
of  small  quartz  grains,  quartz  being  the  most  indestructible  of 
common  minerals.  Some  sandstones  are  well  cemented  and  firm, 
others  friable ;  and  iron  oxide  cement  often  gives  to  them  red, 
yellow,  or  brown  colors. 

A  well-cemented  sandstone  or  conglomerate,  with  much  quartz 
in  it,  is  one  of  the  most  durable  of  rocks,  resisting  denudation  so 
well  that  it  forms  peaks  and  ridges,  as  in  the  Appalachians. 
Since  quartz  does  not  decay  and  produce  plant  food,  as  feldspar 
and  many  other  minerals  do,  sandstones  make  poor  soils. 

Shale,  the  most  common  clay  rock,  varies  in  color  from  black 
to  blue  or  light  gray.  Because  of  the  presence  of  large  numbers 
of  flattened  particles,  often  small  mica  flakes,  it  splits  readily 
along  the  bedding  planes.  Shales  split  so  easily,  and  are  so  soft, 
that  they  readily  disintegrate,  and  among  mountains  are,  there- 
fore, usually  found  in  the  valleys.  Soils  produced  by  the  decay 
of  shale  are  much  more  fertile  than  sandstone  soils. 

Chemically  formed  Rocks.  —  The  decay  of  minerals  produces 
many  substances  which  underground  water  dissolves.  After  being 
carried  for  a  while,  some  may  be  deposited.  For  example,  car- 
bonate of  lime  is  being  deposited  as  stalactites  in  caverns  (p.  60) 
and  as  calcareous  tufa  around  the  Hot  Springs  of  Yellowstone 
l^ark  (Fig.  243).  On  the  coast  of  Florida  and  in  Great  Salt  Lnke 
it  is  also  being  precipitated  in   small,  romiflod.  or  ooh'tio  gniii^s 


4lO 


NEIV  PHYSICAL   GEOGRAPHY. 


(p.  163).  Salt  is  being  deposited  on  marshes  bordering  Great 
Salt  Lake  and  the  Caspian  Sea ;  and,  by  the  drying  up  of  salt 
lakes,  as  in  western  United  States,  gypsum  has  been  precipitated. 
Deposits  of  silica  around  the  geysers  of  Yellowstone  Park  form 
silicious  sinter  (Fig.  244)  ;  and  bog  iron  ore  is  being  accumulated 
where  certain  spring  waters,  on  reaching  the  air,  are  forced  to 
deposit  iron.  Underground  water  has  deposited  many  veins  of 
valuable  metal  in  fissures  in  the  crust  (p.  132). 

Sedimentary  Kocks. 


Oeigin. 

Name. 

Composition. 

Frag- 
mental 
or  clastic 
rocks. 

Gravel  beds. 
Conglomerates. 
Sand  beds. 
Sandstones. 
Clay  beds. 
Shale. 

Made  of  pebbles  derived  from  other  rocks. 

Consolidated  masses  of  pebbles. 

Finer  fragments,  usually  quartz  grains. 

Consolidated  sand  beds. 

Disintegrated  feldspar,  hornblende,  etc. 

Consolidated  clay  beds,  splitting  readily. 

Chemically 

formed 

rocks. 

Stalactite,   oolite, 
calcareous  tufa. 
Iron  deposits. 
Silicious  sinter. 
Salt. 
Gypsum. 

Carbonate  of  lime,  deposited  in  water. 

Some  ores  of  iron,  especially  bog  iron  ore. 
Silica  deposited  from  water. 
Sodium  chloride. 
Sulphate  of  lime. 

Organic 
rocks. 

Most  limestones. 
Coal  (bituminous, 
lignite,  peat). 

Carbonate  of  lime,  made  of  shells,  etc. 
Made  of  plant  remains. 

Organic  Rocks.  —  Carbonate  of  lime,  dissolved  in  water,  supplies 
many  animals  with  materials  for  shells,  or  limy  framework. 
Where  such  animals  aie  abundant,  as  in  coral  reefs  (p.  217), 
their  limy  remains  often  accumulate  as  thick  beds  of  limestone. 
Many  such  beds  have  been  raised  to  form  part  of  the  land. 
Limestone,  being  both  soft  and  soluble,  is  worn  away  to  form 
lowlands ;  and,  since  it  is  rich  in  plant  food,  it  forms  a  fertile 
soil.  This  is  illustrated  in  the  broad,  fertile  limestone  valleys 
which  extend  among  the  mountains  of  New  England  and  New 
Jersey,  and  thence  through  the  Shenandoah  valley  of  Virginia 


I 


ROCKS.  411 

to  Tennessee.  Dolomite  is  not  so  easily  worn,  and,  when  very 
massive,  sometimes  forms  mountains.  One  very  rugged  section 
of  the  Alps  is  known  as  the  Dolomite  Alps. 

Eemains  of  plants  accumulate  in  swamps,  as  in  peat  bogs 
(p.  168),  where  the  water  retards  decay.  When  such  swamp 
deposits  have  been  covered  with  beds  of  other  rocks,  they  gradu- 
ally lose  their  water  and  gases,  and  change  to  coal  (p.  170).  The 
early  stages  of  this  change  form  lignite,  later  stages  bituminous 
coal. 

4.  Igneous  Rocks. — These  rocks,  which  have  risen  in  a  melted 
condition  from  within  the  earth,  have  cooled  either  on  the  surface, 
as  near  volcanoes,  or  below  the  surface  as  intruded  masses  in  the 
crust  (p.  126).  In  the  latter  case,  the  overlying  blanket  of  strata 
has  allowed  the  lava  to  cool  so  slowly  that  the  minerals  have  had 
opportunity  to  grow  to  fair  size,  giving  these  intruded  rocks  a 
coarse  crystalline  structure.  In  many  places  denudation  has 
worn  the  surface  down  to  these  intruded  igneous  rocks. 

Grayiite(¥\g.  33). —  Granite  is  the  most  common  intruded  igneous 
rock.  Of  what  minerals  is  it  composed  (see  table  p.  412)?  The 
structure  is  so  coarse  that  the  different  mineral  gr-^ins  are  plainly 
seen  and  easily  distinguished.  The  color  of  granite  varies  accord- 
ing to  the  color  of  the  feldspar,  being  commonly  light  and  either 
gray,  grayish  green,  red,  or  pink.  It  is  a  valuable  building  stone, 
and  is  one  of  the  hardest  and  most  durable  of  rocks,  resisting 
destruction  so  well  that,  in  the  wearing  down  of  mountains,  it  is 
commonly  left  standing  as  peaks. 

Syenite,  a  coarse-grained  rock,  resembles  granite,  but  has  no 
quartz.  Gabbro,  norite,  and  anorthosite,  found  in  the  Adiron- 
dacks  and  in  Canada,  are  hard,  intruded  igneous  rocks,  less  com- 
mon than  granite. 

Diorite  and  Diabase  are  dark-colored  igneous  rocks  without 
quartz,  the  color  being  due  to  dark-colored  minerals,  especially 
hornblende,  augite,  and  mica.  Diabase,  also  called  traj),  is  often 
so  fine  grained  that  the  minerals  cannot  be  distinguished  without 
a  microscope.  The  Palisades  of  the  Hudson  and  the  trap  hills 
of  New  Jersey  and  the  Connecticut  valley  are  diabase. 

Rhyolite,  trachyte,  andesite,  and  basalt  (see  table)  are  among 
the  most  common  lavas  erupted  from  volcanoes.      The  first  two 


412 


NEW  PHYSICAL   GEOGRAPHY. 


are  light,  the  last  two,  dark  colored.  In  most  cases,  erupted  lavas 
have  cooled  too  rapidly  for  the  mineral  grains  to  grow  large 
enough  to  be  distinguished  by  the  eye  alone ;  but  large  porphyritic 
crystals  are  often  scattered  through  them,  having  been  formed 
while  the  rock  was  still  molten,  then  inclosed  in  the  fine-grained 
mass,  which  quickly  cooled  when  the  lava  reached  the  air. 

Sometimes  lavas  cool  so  rapidly  that  they  resemble  black  glass, 
and  they  are  then  called  natural  glass  or  ohsidiayi. 

A  porous  structure  is  given  lavas  by  the  expansion  of  steam, 
which  forms  cavities ;  and  rapid  expansion  of  the  steam  blows  the 
lava  into  bits,  forming  pumice  (Fig.  33)  and  volcanic  ash  (p.  122). 

The  ash  from  the  Martinique  eruption  (p.  113)  was  andesite  lava 
blown  to  pieces  by  steam  ;  the  lava  of  the  Hawaiian  volcanoes  is  basalt. 
Much  of  the  country  west  of  the  Rocky  Mountains  is  covered  with 
basalt,  andesite,  and  other  lava  rocks  erupted  from  ancient  volcanoes 
and  fissures.  These  lavas,  having  many  cavities  for  water  to  enter,  and 
being  made  of  minerals  that  decay  readily,  are  soon  covered  with  a 
fertile  soil,  for  the  minerals  of  lava  are  rich  in  plant  food. 

Igneous  Rocks. 


Texture. 

Name. 

Chief  Mineral  Components. 

Coarse  grained. 

Granite. 
Syenite. 
Diorite. 

Quartz,  feldspar  (orthoclase),  and 
hornblende,  or  mica,  or  both. 

FeldspaT  (orthoclase)   and  either 
mica,  or  hornblende,  or  both. 

Feldspar  (plagioclase)  and  either 
hornblende,  or  mica,  or  both. 

Both  coarse  and 
fine  grained. 

Diabase. 

Feldspar  (plagioclase)  and  augite. 

Fine  grained. 

Rhyolite       (quartz 

porphyry) . 
Trachyte. 

Andesite. 
Basalt. 

Quartz,  feldspar  (orthoclase),  and 

hornblende,  or  mica,  or  both. 
Feldspar  (orthoclase),  and  either 

hornblende,  or  mica,  or  both. 
Feldspar  (plagioclase),  and  either 

hornblende,  mica,  augite,  or  two 

of  these. 
Feldspar  (plagioclase),  and  augite 

(often  olivine). 

ROCKS. 


413 


5.  Metamorphic  Rocks. — Any  rock  subjected  to  great  pressure,  as 
m  mountain  folding,  and  to  the  action  of  heated  water,  is  certain 
to  suffer  change  or  metamorphism.  In.  sandstone,  for  example, 
silica  may  be  deposited  around  the  grains  until  the  rock  becomes 
almost  one  solid  mass  of  quartz,  called  quartzite.  Shale,  when 
altered  by  metamorphism,  changes  to  slate.  New  minerals  are 
then  developed,  which  have  cleavage  so  perfect  that  the  slate  is 
caused  to  split,  or  cleave  readily.  By  metamorphism  limestone  is 
changed  to  crystalline  calcite,  as  in  the  case  of  white  marble. 

In  the  Appalachian  Mountains  (p.  109),  coal  has  been  metamor- 
phosed to  anthracite.  In  Ehode  Island,  where  mountain  folding 
was  even  more  intense,  coal  has,  in  some  cases,  been  changed 
to  graphite,  which  is  pure  carbon. 

When  subjected  to  metamorphism  so  intense  that  the  minerals 
have  recrystallized,  some  rocks  are  altered  to  gneiss.  Gneiss 
resembles  granite ;  but  there  is  a  slight  banding  of  the  minerals 
(Fig.  33),  due  to  the  fact  that  they  have  developed  along  lines  of 
least  resistance  —  that  is,  at  right  angles  to  the  pressure.  Where 
the  banding  is  so  distinct  that  the  rock  readily  cleaves,  it  is  a 
schist.  Gneisses  and  schists  are  durable  crystalline  rocks,  found 
in  regions  of  intense  mountain  folding. 

Metamorphic  Eocks. 


'Sa.me. 

SotTECE. 

Mineral  Composition. 

Quartzite. 

Altered  sandstones. 

Quartz. 

Slate  (argillite). 

Altered  clay  rocks. 

Partially  crystallized  mica- 
ceous minerals  developed 
out  of  the  clay  particles. 

Marble. 

Altered  carbonate  of  lime. 

Calcite. 

Anthracite 

Altered  coal. 

Mainly  carbon   and  carbon 

(graphite). 

compounds. 

Schist. 

Altered     from      various 

Variable  —  usually   two    or 

rocks,  e.g.  shale,  con- 

more   of    the    following : 

glomerate,  diorite,  etc. 

feldspar,  quartz,  horn- 
blende, or  mica. 

Gneiss. 

Altered      from     various 

Variable  —  usually    two    or 

rocks,  e.g.  shale,  con- 

more   of    the    following : 

glomerate,         granite, 

feldspar,     quartz,     horn- 

diorite, etc. 

blende,  or  mica. 

414 


NEW  PHYSICAL    GEOGRAPHY. 


Suggestions.  —  (1)  Collect  minerals  from  your  neighborhood  and 
study  them.  Dana's  Minerals  and  How  to  Study  Them  is  a  good  book  of 
reference.  (2)  Collect  rocks  from  the  ledges,  bowlders,  quarries,  and 
stone  yards.  If  you  live  in  a  part  of  the  country  reached  by  the  ice 
sheet  (Fig.  270),  you  will  find  a  varied  store  of  rock  specimens  in  the 
gravel  banks.  See  how  many  kinds  you  can  collect.  Study  their  char- 
acteristics ;  place  them  in  one  of  the  three  groups  and,  if  possible,  give 
them  their  proper  names.  The  teacher  can  systematize  this  work  and 
make  it  of  great  disciplinary  value.  (3)  Place  pieces  of  quartz,  feld- 
spar, and  calcite  in  weak  hydrochloric  acid.  Which  .■  .ittacked  by  it? 
Water  in  the  earth  is  often  weakly  acid,  and  in  this  state  attacks  min- 
erals. (4)  Grind  up  some  mica,  mix  with  sand,  and  stir  in  water.  After 
the  sediment  has  settled,  notice  the  position  of  the  mica  flakes.  It  is  for 
this  reason  that  shales  split  readily  along  the  bedding  planes.  (5)  To 
which  of  the  three  groups  do  the  rocks  of  your  neighborhood  belong? 
What  kind  or  kinds  do  you  find  ?  Of  what  are  they  made  ?  Are  they 
hard  or  soft?  Do  they  make  rich  or  poor  soil?  If  your  home  is  in  a 
valley,  see  if  the  rocks  on  the  hills  are  different.  What  are  the  differ- 
ences ?     Do  they  help  account  for  the  hills  and  valleys  ? 

Table  for  Guide  in  Study  of  Minerals. 


Name. 

Hard- 
ness. 

Color. 

Specific 
Gravity. 

Crystal 
Form. 

Cleav- 
age. 

Frac- 
ture. 

Lus- 
ter. 

Other 
Feat- 
ures. 

Quartz. 

7 

Trans- 
parent. 

2.6 

Hexag- 
onal. 

None. 

Con- 
choidal. 

Vitre- 
ous. 

Calcite. 

Etc. 

1 

Reference  Books.  —  Dana,  Minerals  and  How  to  Study  Them,  Wiley  & 
Sons,  New  York,  1895,  .|1.50 ;  Kemp,  Handbook  of  Rocks,  D.  Van  Nostrand 
Co.,  New  York,  2d  ed.,  1900,  ^1.50. 


APPENDIX    D.     GEOLOGICAL   AGES. 


While  it  is  impossible  to  tell  the  age  of  the  earth  in  years 
(p.  45),  geologists  have  divided  the  strata  into  stages,  or  periods, 
and  have  determined  their  relative  age.  This  is  made  possible  by 
the  fossils  the  strata  contain.  For  example,  there  was  a  time 
when  no  animals  higher  than  fishes  lived  on  the  earth;  and  if 
strata  contain  remains  of  birds,  it  is  certain  that  they  were  not 
deposited  in  those  ancient  times.  Careful  studies  of  fossils,  in 
all  parts  of  the  earth,  have  so  clearly  revealed  the  history  of  the 
development  of  life  that,  on  examining  the  fossils  in  a  rock,  geolo- 
gists can  now  tell  in  what  period  it  was  formed.  To  the  different 
periods  names  have  been  given,  some  of  the  most  common  of 
which  are  placed  in  the  following  table  : 


CENOZOIC 

Pleistocene,  or 
Quaternary . 

Mail  assumes  importance,  particularly  in 
upper  part.     Glacial  period  in  first  half. 

TIME. 

(Age  of 

NEOCENE. 

Mammals  develop  in  remarkable  variety, 

Mammals.) 

EOCENE. 

and  to  great  size,  while  reptiles  diminish. 

MESOZOIC 

Cretaceous. 

Birds  begin  to  be  important;  reptiles  con- 
tinue ;  and  higher  mammals  appear ;  land 
plants  and  insects  of  high  type. 

TIME. 

(Age  of 

Jurassic. 

Reptiles  and  amphibia  predominate. 

Reptiles.) 

Triassic. 

Amphibia  and  reptiles  develop  remarkably ; 
low  forms  of  mammals  appear. 

Carboniferous. 

Land  plants  assume  great  importance. 

PALEOZOIC 
TIME. 

Devonian. 

Fishes  are  abundant. 

(Age  of 
Invertebrates.) 

Silurian. 

Invertebrates  ^  prevail. 

Cambrian. 

No  forms  higher  than  invertebrates. 

In  part 
AZOIC  TIME. 

(No  fossils 
known.) 

Archean.^ 

Mostly  metamorphic  rocks;  perhaps,  in 
part,  original  crust  of  earth. 

1  Invertebrates  continue  abundant  to  present  time,  but  are  of  different  kinds.     Fishes,  whicti 
began  in  the  Silurian,  continue,  though  with  many  changes,  to  the  prcise^t  time. 

2  Upper  part  sometimes  called  Algonkian. 

415 


APPENDIX   E.     TIDES. 


The  full  explanation  of  tides  is  considered  too  difficult  and 
complex  for  statement  in  so  elementary  a  book.  It  is  known  that 
they  are  caused  by  the  attraction  of  gravitation  which  both  sun 
and  moon  are  exerting  on  the  earth ;  but  the  moon  is  more 
effective  in  this  than  the  sun. 

This  pull  of  gravitation  draws  the  ocean  water  toward  the  moon 
(Fig.  557),  producing  a  wave  which  follows  the  moon  across  the 

oceans.  A  second  high  tide  is  formed 
on  the  opposite  side  of  the  earth.  In 
this  way  the  ocean  is  distorted  into 
a  somewhat  elliptical  form.  If  the 
earth  were  all  water,  the  attraction 
of  the  moon  would  change  it  to  an 
ellipse  ;  and,  as  the  earth  rotated,  the 
form  of  the  ellipse  would  constantly 
change  to  keep  its  axis  pointing  to- 
ward the  moon.^  That  is  to  say,  two 
waves  would  constantly  be  passing 
around  the  earth,  following  the  moon. 
To  understand  this  shape  attach  a 
rubber  ball  to  the  floor  and,  by  a 
string  on  the  upper  side,  pull  until 
the  ball  loses  its  spherical  shape. 

Tidal  waves  are  produced  by  the 
sun    in    the    same    way   as    by    the 
moon ;  but,  although  the  sun  is  so  much  larger  than  the  moon, 


Fig.  557.  —  Uistortion  of  ocean 
by  attraction  of  moon, —  dis- 
tortion being  greatly  exag- 
gerated. 


1  There  is  more  to  the  tidal  explanation  than  the  mere  pull  of  gravitation; 
there  is  also  the  effect  of  centrifugal  force.  However,  unless  the  teacher, 
because  of  special  interest,  wishes  to  enter  into  a  full  study  of  tides,  it  does 
not  seem  well  to  introduce  this  complex  question. 

416 


TIDES. 


417 


rts  greater  distance  makes  its  tide-producing  effect  less.  The 
solar  tides  are,  therefore,  only  about  one  third  as  great  as  the  lunar 
tides.  Thus,  at  all 
times,  there  are  four 


tUNARTlOE, 


tidal  waves   in   the      © 


oceans,  two  formed 
by    the   moon,    and 


>0LAKT10t 


© 


SOIABTIBE  LUNAR  not 

Fig.  558.  —  To  illustrate  cause  of  spring  tides  —  dis- 
tortion being  greatly  exaggerated. 


ViM.f\  TIDt 


SOUR  TIDE 


SOLAR  TIOE 


© 


two  smaller  ones  by 
the  sun.  In  each 
pair  one  is  on  the  opposite  side  of  the  earth  from  the  other. 

At  full  moon  (Fig.  558)  the  sun  and  moon  are  nearly  in  line. 

They  are  then  pulling  so  nearly  together  that  the  solar  and  lunar 

tides  combine,  causing  an  uncommonly  high  tidal  range,  known  as 

P^  spring  tide.     At  new 

moon,  the  sun  and 
moon  are  again 
nearly  in  line,  and 
spring  tides  are 
again  formed.  Dur- 
ing the  quarters 
(Fig.  559),  on  the 
other  hand,  the  high 
tides  formed  by  the 
moon  occur  where 
low  tides  are  caused  by  the  sun ;  consequently  the  tidal  range  is 
much  less.  These  tides  of  low  range  are  called  neap  tides.  Each 
lunar  month,  that  is  every  29^  days,  there  are  two  spring  and  two 
neap  tides. 

Another  cause  for  variation  in  tidal  range  is  the  distance  of  the  moon. 
The  moon  revolves  around  the  earth  in  an  ellipse,  and  when  it  is  nearest 
to  the  earth,  or  in  perigee^  the  lunar  tide  is  higher  than  when  it  is  farthest, 
or  in  apogee.  Because  of  these  variations  in  the  relative  position  of  sun 
and  moon,  and  in  the  distance  of  "the  moon,  the  tidal  range  varies  greatly. 
There  is  also  an  irregular  variation  due  to  wind  (p.  271),  which  some- 
times piles  the  water  up  in  bays,  causing  it  to  overflow  wharves  and  low 
land  that  the  tide  itself  never  reaches. 


LUNAR  TlOe 

Fig.  559.  —  To  illustrate  cause  of  neap  tides. 


2b 


APPENDIX  F.     MAGNETISM. 

In  the  United  States,  as  in  other  regions,  a  bar  or  needle  of 
magnetized  steel,  so  suspended  that  it  freely  swings  horizontally, 
will  point  north  and  south.  An  instrument  having  such  a  needle 
is  a  compass.  Throughout  most  of  the  country  the  compass  needle 
points  a  little  to  one  side  of  a  true  north  and  south  line.  In  central 
western  Greenland  the  needle  points  westward,  in  northern  Green- 
land, south  westward.  The  place  toward  which  the  compass  needle 
points  is  known  as  the  north  magnetic; pole,  and  is  located  north 
of  Hudson  Bay  and  west  of  Baffin  Land.  Within  the  Antarctic 
Circle,  between  New  Zealand  and  the  South  Pole,  there  is  a 
similar  region  known  as  the  south  magnetic  pole. 

It  is  because  of  these  centers  of  magnetism  that  the  compass  is 
so  valuable  that  sailors  depend  upon  it  for"  determining  the 
course  of  their  ships,  and  the  steersman  always  has  one  in  plain 
sight.  In  the  Arctic  the  comj^ass  is  much  less  useful,  for,  though 
nearer  the  magnetic  pole,  the  needle  is  less  sensitive  and  more 
easily  deflected  by  outside  influences,  such  as  the  presence  of  iron. 

The  reason  for  this  fact  is  that  the  cause  for  the  attraction  of  the 
needle  lies  beneath  the  earth's  surface.  This  is  proved  by  so  suspending 
a  needle  that  it  will  freely  swing,  or  dip,  vertically.  At  the  magnetic 
pole,  the  needle  of  such  a  dip  compass  points  directly  downward ;  near 
the  equator  it  swings  horizontally ;  part  way  between  the  pole  and  equa- 
tor it  points  toward  the  earth  at  an  angle.  From  this  it  is  evident  that, 
the  nearer  one  goes  to  the  magnetic  pole,  the  stronger  becomes  the  down- 
ward attraction  and  the  weaker  the  horizontal  pull,  and,  therefore,  the 
less  useful  the  compass. 

Along  a  line  extending  from  South  Carolina  to  Lake  Superior, 
magnetic  north,  or  north  by  the  compass,  is  the  same  as  true  north  ; 
that  is,  the  compass  points  toward  the  north  pole.  East  of  this 
line  the  compass  points  to  the  west  of  true  north,  northern  Maine 
showing  a  difference  between  magnetic  and  true  north,  or  a  declina- 

418 


v^-xL-J 

C 

r 
m 

1  1 

VIAItl.GAUaE 


XtrbOTrtoX  5M«<M«»f; 


Fig.  561.  —  Rain  gauge.    B,  outer  cylinder;  (7,  inner  cylinder;  a,  a  (and  small 

right-hand  figures),  the  funnel. 


Fig.  562.  —  Hachure  map  from  one  of  the  United  States  Coast  Survey  charts. 


Fig.  5();i.  —  To  illustrate  the  meaning  of  contours.     On  the  left  is  a  model ;  on  th^ 
right  the  same  topography  is  represented  hy  contours. 


MAGNETISM.  419 

Hon,  of  21°.  West  of  the  line  of  no  variation,  or  no  declination, 
the  needle  points  to  the  east  of  true  north,  in  northern  Washing- 
ton reaching  an  east  declination  of  23°.  A  map  showing  lines  of 
equal  magnetic  declination  is  an  isogonic  map  (Fig.  560). 

The  amount  of  declination  slowly  changes,  so  that  a  map  made 
for  one  year  is  not  strictly  accurate  for  the  next  year ;  but  the 
change  is  so  slow  that  a  long  time  is  necessary  to  produce  a 
marked  difference.  The  cause  for  these  changes,  and  even  the 
cause  for  the  magnetism  of  the  earth,  is  unknowai.  It  is  some 
condition  within  the  earth,  far  from  the  surface,  possibly  in  some 
way  connected  with  the  heated  interior.  All  that  is  positively 
known  is  that,  for  some  reason,  the  earth  acts  as  a  great  magnet. 

The  aurora  horealis,  or  northern  lights,  is  in  some  way  connected  with 
this  magnetism.  A  similar  phenomenon,  the  aurora  australis,  is  found  in 
the  southern  hemisphere.  The  aurora  is  not  common  in  the  United 
States,  though  sometimes  it  becomes  visible,  and  even  vivid.  The  north- 
ern sky  is  then  aglow  with  an  arch  of  strange  light,  with  streamers  dart- 
ing to  and  fro.  In  the  far  north  the  aurora  becomes  much  more  vivid, 
and  maybe  seen  night  after  night.  The  cause  of  the  aurora  is  unknown, 
though  it  seems  to  be  due  to  faint  electrical  discharges  in  the  upper  air> 
resulting  from  some  influence  of  the  earth's  magnetism. 

Suggestions.  —  (1)  Learn  to  read  a  compass  (a  small  one  is  quite 
inexpensive).  Determine  the  true  north  and  south  line.  This  can  be 
done  by  setting  up  two  poles  in  line  with  the  north  star.  With  a  com- 
pass, observe  the  difference  between  true  and  magnetic  north.  (2)  Place 
a  bar  of  iron  near  a  compass.  Is  the  needle  disturbed?  Try  the  effect 
of  a  magnet.  (3)  If  you  have  ever  seen  an  aurora,  describe  it.  Have 
you  ever  read  a  description  of  one  in  a  book  of  Arctic  travel  ? 


APPENDIX    G.     METEOROLOGICAL    INSTRU- 
MENTS. 


1.  Thermometers.  —  The  ordinary  thermometer  is  a  sealed 
glass  tube  with  a  cavity  of  small  diameter,  ending  below  in  an 
expansion,  or  bulb,  in  which  there  is  mercury.  The  mercury  can 
rise  and  fall  freely  in  the  tube  because  there  is  no  air  in  it. 
The  principle  of  the  thermometer  is  that  liquids,  like  mercury, 
expand  and  require  more  space  when  warmed,  but,  when  cooled, 
contract  and  take  up  less  space.  As  the  temperature  changes, 
therefore,  the  mercury  in  the  bulb  causes  a  tiny  thread  of  mercury 
to  rise  and  fall  in  the  tube.  Other  liquids  may  be  used ;  in  fact, 
alcohol  is  used  when  thermometers  are  to  be  exposed  to  cold 
greater  than  the  freezing  point  of  mercury  (—  40°). 

Thermometers  are  graduated  in  degrees,  the  division  commonly  used 
in  America  and  England  being  the  Fahrenheit  (Fahr.)  scale.  In  this, 
the  boiling  point  of  water  is  placed  at  212^  and  its  freezing  point  at  32°. 
This  is  not  nearly  so  simple  a  scale  as  the  Centigrade  (Cent.)  which  i& 

commonly  used  on  thfe 
continent  of  Europe.  In 
this,  the  freezing  point  is 
placed  at  0°  and  the  boil- 
ing point  at  100^  To 
convert  Centigrade  to 
Fahrenheit,  multiply  by 
1.8°  and  add  32°.  Thus 
10°  Cent,  equals  50°  Fahr. 
(10°  X  1.8°  =  18°+  32°  = 
50°). 

Metals      also     expand 
Because  of  this  fact,  thermom- 


i^'iG.  o()4.  —  A  Uitji'iiiograpli. 


when  warmed  and  contract  when  cooled, 
eters  may  be  made  of  metal  strips  connected  with  a  hand  that  moves 
-iver  a  graduated  dial.  Such  thermometers  may  sometimes  be  seen  in 
tront  of  city  stores.  A  metal  thermometer  may  also  be  connected  with 
an  arm,  bearing  a  pen,  which  is  moved  as  the  temperature  changes. 
This  pen  may  be  so  placed  as  to  press  against  a  piece  of  paper  on  a, 
cylinder,  revolved  by  clockwork.     As  the  pen  rises  and  falls,  while  the 

420 


METEOROLOGICAL  INSTRUMENTS.  421 

cylinder  regularly  revolves,  it  writes  a  record  of  temperature  changes  for 
every  minute  of  the  day.  Such  a  self-recording  thermometer  is  called  a 
thermograph  (Fig.  564). 

2.  Barometers.  —  The  weight,  or  pressure,  of  air  will  push 
liquid  up  into  a  tube  having  a  vacuum  in  the  top.  It  will  push 
the  liquid  up  until  a  column  is  formed  that  equals  the  weight  of 
the  air  column  pressing  on  it.  It  is  because  of  this  air  pressure 
that  water  is  pushed  up  from  a  well  into  the  tube  of  a  pump. 
The  stroke  of  the  pump  exhausts  air  from  the  tube,  thus  tending 
to  make  a  vacuum,  into  which  the  water  may  be  pushed  by  the 
air  pressure.  Since  a  column  of  water  about  30  feet  high  bal- 
ances the  air  pressure,  an  ordinary  pump  could  not  possibly  raise 
water  from  a  fifty-foot  well. 

Years  ago  water,  in  tubes  over  30  feet  long,  was  used  to  measure 
air  pressure.  Mercury  is  now  employed'  because  it  is  so  heavy 
that  a  column  only  thirty  inches  high  balances  the  air  pressure. 
An  instrument  containing  such  a  mercury  column  is  called  a 
barometer. 

Any  one  can  make  a  rough  barometer  with  a  glass  tube  35  inches 
long,  sealed  at  one  end.  Fill  it  with  mercury,  and  invert  it,  with  the 
open  end  in  a  sinall  dish  of  mercury,  being  careful  not  to  allow  the 
mercury  to  spill.  The  mercury  will  fall  a  few  inches,  and  air  pressure 
will  keep  it  there.  By  fastening  it  to  a  standard  to  keep  it  upright,  one 
may  watch  the  mercury  rise  and  fall  from  day  to  day.  A  scale  of  inches 
and  tenths  of  inches  may  be  marked  on  the  glass  with  a  piece  of  quartz  or 
a  glazier's  diamond ;  or  on  the  piece  of  wood  to  which  the  tube  is  fas- 
tened.    By  comparison  with  a  barometer  the  scale  may  be  made  exact. 

Ordinary  mercury  barometers  are  graduated  in  inches  and 
tenths  of  inches,  and  a  scale,  called  a  vernier,  enables  readings  to 
hundredths  of  inches.  As  storms  come  and  go  the  air  pressure 
varies,  and  with  these  changes  the  height  of  the  mercury  column 
changes.  When  the  air  is  heavy  the  barometer  column  is  high, 
and  there  is  a  high  barometer  ;  when  the  air  is  light  the  barometer 
column  is  low,  and  there  is  a  low  barometer.  For  example,  30.1 
inches  is  a  high  barometer  ;  29.3  is  a  low  barometer. 

Since  there  is  less  air  (and  therefore  less  pressure)  above  high 
lands  than  lowlands,  the  barometer  is  low  on  highlands  and  higk 
on  lowlands.     As  this  differ&nce  in  pressure  varies  quite  regu. 


422 


NEW  PHYSICAL   GEOGRAPHY. 


larly,  a  barometer  may  be  used  to  measure  elevation  ;  for  a,  cnange 
of  an  inch  in  the  mercury  column  represents  a  difference  in 
elevation  of  a  certain  number  of  feet. 

A  mercurial  barometer  is  too  cumbersome,  and  too  easily  in- 
jured, to  be  carried  about; 
therefore,  for  measuring  ele- 
vations, an  aneroid  barometer 
is  commonly  used.  An  ane- 
roid, which  is  so  small  that  it 
may  be  carried  in  the  pocket, 
has  a  metal  diaphragm  inside 
of  a  metal  case.  Differences 
in  air  pressure  cause  this  dia- 
phragm to  move,  and  this  move- 
ment is  communicated  to  a 
hand  which  moves  over  a  dial 
(Fig.  565).  Since  the  dial  is 
graduated  in  feet,  one  can  tell 
at  a  glance  how  high  he  has 
climbed. 

One  serious  disadvantage  in  the 
use   of   the  aneroid  is  that  it  is 
affected  by  all  changes  in  air  pres- 
sure.     Thus,   if   a   storm    passes 
while  the  aneroid  is  being  used 
to  measure  an  elevation,  the  change 
in  air  pressure  causes  the  hand  to  move,  making  an  error  in  the  obser- 
vation.    This  can  be  corrected,  however,  by  comparing  its  readings  with 
those  of  another  barometer  kept  at  a  fixed  place. 

As  in  the  case  of  thermometers,  there  are  self-recording  barometers,  or 
barographs.  In  these,  as  in  thermographs,  a  pen  point  pressed  against  a 
roll  of  paper  on  a  cylinder,  revolved  by  clockwork,  gives  a  continuous 
record  of  changes  in  pressure. 

3.  Anemometers.  —  Wind  direction  is  determined  by  the  ordinary 
weather  vane,  and  the  rate  at  which  the  air  is  moving  by  the 
aneraometer  (Fig.  566).  The  latter  instrument  consists  of  four 
metal  cups  on  crossbars,  revolved  by  the  wind  striking  the 
hollow   side   of    the    cups.     Each    revolution   is    communicated 


Fig.  565.  —  Aneroid  barometer,  gradu- 
ated in  feet  (outside)  and  inches 
(inside). 


METEOROLOGICAL  INSTRUMENTS. 


423 


to  a  cog-wheel,  which  causes  a  hand  to  move  on  a  dial,  recording 
the  velocity. 

Wind  velocity  is  measured  in  miles  per  hour,  and  the  dial  is  so 
graduated  that  the  hand  indicates  the  number  of  miles  the  wind 
has  moved.  An  anemometer  may  be  connected  by  electric  wire 
to  a  self-recording  apparatus. 

A  slight  breeze  has  a  velocity  of  from  1  to  10  miles  per  hour ; 
a  strong  wind  from  20  to  30  miles ;  a  gale  from  40  to  60  miles ; 
and  a  tornado  wind  even  as  much  as  200  miles  per  hour. 

4.  Measurement  of  Vapor.  —  There  are  several  instruments  for 
determining  the  humidity  of  the  air.  One  of  these  is  the  hair 
hygrometer,  which  consists  of  a  bundle  of  hair  robbed  of  its  oil. 
8uch  hair  will  absorb  vapor,  changing  in  length  as  the  amount  of 
absorbed  vapor  varies.  It  is 
because  of  this  fact  that  the 
"iiair  of  many  people  becomes 
straight  in  damp  weather.  In 
the  hair  hygrometer  a  hand  is 
moved  over  a  graduated  scale, 
in  one  direction  if  the  humidity 
is  high,  in  the  other  if  it  is 
low. 

Another  instrument,  the 
sling  psychrometer,  consists  of 
two  thermometers  attached  to 
a  board,  one  having  a  piece  of 
wet  muslin  around  its  bulb. 
Its  use  depends  upon  two 
facts :  (1)  That  evaporation 
is  more  rapid  in  dry  than  in 
humid  air ;  (2)  that  evapora- 
tion lowers  the  temperature. 

Since  evaporation  is  more  rapid  when  the  air  is  moving,  th( 
sling  psychrometer  is  whirled  around  for  a  minute  or  two.  If  tlu 
air  is  saturated,  there  will  be  no  evaporation  from  the  wet  muslin, 
and  the  two  thermometers  will,  therefore,  read  the  same ;  but  if 
the  air  is  dry,  the  wet  bulb  thermometer  will  register  a  perceptibly 
lower  temperature.     The  United  States  Weather  Bureau  furnishes 


Fig.  566.  —  An  anemometer. 


424  NEW  PHYSICAL   GEOGBAPHT, 

tables  from  which  the  relative  humidity  can  be  calculated,  when 
the  difference  in  temperature  between  the  dry  and  wet  bulb  ther^ 
mometers  has  been  determined. 

Various  instruments  are  used  for  determining  the  rate  of  evaporation, 
which  varies  from  day  to  day  and  from  place  to  place.  An  evaporating 
pan  consists  of  a  dish  of  water  in  which  is  placed  a  ruler  graduated  in 
inches  and  tenths  of  inches.  By  this,  one  can  tell  how  much  is  evapo- 
rated from  the  water  surface  in  a  given  time.  Rain  should  be  prevented 
from  falling  into  the  pan,  but  it  should  be  freely  open  to  the  air.  It 
should  not  be  exposed  to  the  sun,  because  warming  increases  evaporation. 
It  is  best  to  place  it  in  the  ground  with  the  top  level  with  the  surface. 

5.  Rainfall  Measurement.  —  Rainfall  is  recorded  in  number  of 
inches  and  tenths  of  inches  that  falls  on  a  given  surface.  Any  cyl- 
inder, as  a  tomato  can,  could  be  used  as  a  rain  gauge,  or  measurer ; 
but  an  ordinary  rainfall  is  so  slight  that  it  would  be  difficult  to 
measure  it  unless  some  provision  were  made  for  collecting  the 
water  in  a  smaller  space  than  the  surface  on  which  it  fell. 

Any  tinsmith  can  make  a  rain  gauge,  with  two  cylinders,  one  inside  of 
the  other,  the  inside  cylinder  having  an  area  of  2.53  inches,  the  out- 
side one  8  inches  (Fig.  561).  A  funnel  fits  over  the  outside  cylinder,  and 
a  hole  in  it  leads  into  the  inside  cylinder.  The  rain  that  falls  on  the 
funnel  collects  in  the  bottom  of  the  inner  cylinder  to  a  depth  ten  times 
that  of  the  actual  rainfall.  Measuring  this  with  a  ruler,  and  dividing  by 
ten,  gives  the  actual  rainfall,  even  though  it  is  slight.  There  are  also 
self-recording  rain  gauges. 

Instruments  are  sometimes  used  for  measuring  snowfall ;  but  usually 
this  can  be  fairly  well  done  by  measuring  its  depth  in  some  place 
where  it  is  not  drifted.  The  average  snowfall  is  about  ten  times  the 
amount  that  would  have  fallen  as  rain.  In  weather  records  it  is  cus- 
tomary to  record  snowfall  in  inches  of  rain.  Place  snow  in  a  cylinder, 
filling  it  to  a  depth  of  a  foot,  and  melt  it  to  see  how  much  water  it  pro- 
duces.    Do  not  pack  the  snow  down. 

6-  An  Instrument  Shelter.  — In  order  to  get  good  results,  meteorologi- 
cal instruments  must  be  placed  where  they  are  not  influenced  by  local  con- 
ditions. For  example,  two  thermometers,  one  in  the  shade,  the  other 
exposed  to  the  sun,  will  give  very  different  readings.  A  simple  instrument 
shelter,  made  of  inclined,  overlapping  slabs,  far  enough  apart  to  let  the 
air  circulate  freely,  and  yet  near  enough  together  to  keep  the  sun  out,  is 
easily  made.     It  should  be  placed  either  on  open  ground  or  on  the  roof. 


METEOROLOGICAL  INSTRUMENTS. 


425 


The  barometer  may  be  kept  in  the  schooh'oom,  the  rain  gauge  on  open 
ground  away  from  a  building,  and  the  anemometer  on  the  roof ;  but  the 
other  instruments  are  best  kept  in  an  instrument  shelter. 

Suggestions. — For  purchase  of  meteorological  instruments,  see  p.  438. 
As  indicated  above,  it  is  possible  to  make  several  of  the  common  instru- 
ments, especially  the  barometer,  psychrometer,  evaporating  pan,  and  rain 
gauge.  This  might  easily  be  done  in  the  manual  training  department. 
AVith  these  instruments  daily  records  may  be  kept,  and  laboratory  work 
of  value  done,  especially  for  comparison  with  the  study  of  weather  maps 
and  storms.  Daily  and  seasonal  temperature  curves  may  also  be  made. 
If  this  work  is  carried  along  with  the  study  of  the  atmosphere,  the  teacher 
will  find  many  opportunities  for  connecting  observations  with  facts  in  the 
book.  For  example,  observe  the  humidity  of  the  air  near  the  ground 
when  dew  is  forming  and  when  it  is  not.  When  frost  is  forming,  take  the 
temperature  of  the  ground  and  of  the  air  10  feet  above  it  to  see  if  radia- 
tion cools  the  ground.  After  the  barometer  begins  to  fall,  does  it  rain  ? 
What  change  in  wind  direction  then  takes  place?    In  temperature,  etc.? 

Suggested  Eecord. 


January  1,  1903. 

January  2, 

1903. 

Janttaet  3,  ' 

1903. 

8  A.M. 

1  P.M. 

8  p.m. 

8  A.M. 

1  P.M. 

8  P.M. 

8  A.M. 

1  P.M. 

8  p.m. 

Temperature 

5° 

10° 

2° 

-1° 

20° 

18° 

17° 

30° 

31° 

Barometer 

30.0 

30.0 

30.1 

30.1 

30.0 

29.9 

29.8 

29.7 

29.6 

Wind 

West 

West 

Calm 

Calm 

S.W. 

S.W. 

South 

S.E. 

East 

Wind  Force 

Moder- 
ate 

Strong 

Calm 

Calm 

Light 

Breeze 

Light 

Strong 

Gale 

Sky 

Clear 

Cumu- 
lus 

Clear 

Clear 

Clear 

Cirrus 

Cirrus 

Cirro 

stratus 

Stratus 

Eainfall 

0 

0 

0 

0 

0 

0 

0 

.1  light 
snow 

.3  heavy 
snow 

Humidity 

80 

60 

82 

85 

55 

85 

90 

100 

100 

APPENDIX   H.       WEATHER   MAPS. 

The  U.  S.  Weather  Bureau  issues  daily  maps  showing  weather 
conditions  throughout  the  country.  By  application  these  can 
doubtless  be  secured  for  the  school,  and,  being  placed  in  the 
schoolroom,  will  serve  as  a  valuable  basis  for  laboratory  study. 

The  weather  maps  are  based  upon  reports  telegraphed  from 
Weather  Bureau  Stations  in  all  sections  of  the  country ;  and  the 
facts  regarding  temperature,  rainfall,  and  wind  are  placed  in  a 
table  at  the  bottom  of  the  map.  On  the  basis  of  these  reports, 
predictions  for  the  next  day  are  made  at  a  central  office. 

On  the  map,  which  is  an  outline  map  of  United  States,  the  direction 
of  the  wind  is  indicated  by  arrows.  At  the  ends  of  some  of  the  arrows  is 
the  letter  R,  meaning  rain,  or  S,  meaning  snow.  Arrows  that  terminate 
in  blank  circles  ($)  mean  clear  weather;  when  crossed  by  a  line  (^), 
partly  cloudy;  and  when  occupied  by  a  cross  ($),  cloudy.  The  centers 
of  high  and  low  pressure  areas  are  indicated  by  the  words  High  and  Low. 
Dotted  lines  (isothermal  lines)  pass  through  places  having  equal  tempera- 
tures, and  continuous  lines  (isobaric  lines)  pass  through  places  with  equal 
air  pressure.  The  barometric  readings  (29.8,  30.1,  etc.)  are  all  reduced 
to  sea  level ;  that  is,  made  to  read  as  they  would  if  the  station  were  at 
sea  level. 

Thus  the  weather  maps,  besides  describing  the  weather  conditions 
and  predicting  for  the  next  day,  contain  a  large  amount  of  information 
concerning  the  weather  of  different  sections.  A  study  of  the  maps  on 
several  successive  days  will  make  their  meaning  plain,  and  will  illustrate 
many  points  discussed  in  the  book. 

Sets  of  maps  suitable  for  the  work  suggested  below  are  easily  obtained 
by  keeping  the  maps  for  a  year  or  two.  Out  of  date  sets  may  possibly  be 
obtained  from  the  Weather  Bureau.  Or  the  teacher  could  make  large 
wall  maps  for  class  use,  selecting  typical  sets,  and  sketching  the  weather 
conditions  on  a  large  outline  map  of  United  States. 

Suggestions. —  (1)  Study  a  weather  map  to  understand  its  meaning. 
Which  isotherm  passes  nearest  your  home?  What  other  places  have  the 
same  temperature  ?  What  is  the  air  pressure  ?  What  other  places  are 
on  the  same  isobar  ?  Is  the  weather  at  your  home  clear,  cloudy,  or  rainy  ? 
What  is  the  wind  direction?     How  do  these  facts  compare  with  your 

120 


WEATHER  MAPS.  427 

own  observations  the  previous  day  ?  Study  the  weather  maps  for  the 
next  two  days.  What  differences  are  noticed?  Do  you  find  any  expla- 
nation ?  (2)  Select  weather  maps  to  illustrate  a  typical  storm.  Have 
each  student  make  a  copy  of  it  on  a  blank  map  of  United  States.  Have 
them  tell  in  what  parts  the  pressure  is  low,  and  where  high.  Shade  between 
the  isobars.  Shade  on  the  map  the  rainy  or  snowy  sections.  With 
another  colored  pencil,  mark  the  cloudy  areas.  What  is  the  direction  of 
the  winds  in  the  diiferent  areas?  What  part  of  the  storm  area  is  warm- 
est? What  part  coolest  ?  What  is  the  direction  of  the  wind  in  each 
case?  Can  you  find  an  explanation  of  any  of  the  facts  observed?  (3)  In 
the  same  way,  study  the  weather  maps  for  the  next  three  days.  Write 
a  statement  of  the  changes  that  have  occurred.  On  an  outline  map 
draw  the  path  followed  by  the  storm  center.  Select  some  place  on  the 
map,  and  have  the  students  describe  the  weather  changes  —  pressure, 
temperature,  wind,  and  rain  —  for  the  four  days.  (4)  In  the  same  way 
study  a  set  of  maps  in  which  a  typical  high  pressure  area,  or  anticyclone, 
passes  across  the  country.  (5)  On  an  outline  map  plot  around  the  same 
central  point  the  winds  of  three  well-defined  storms.  Also  three  anti- 
cyclones. What  about  their  direction  ?  (6)  Give  to  each  student  a  map 
with  a  well-defined  storm,  and  have  him  tell  what  he  thinks  the  weather 
conditions  were  the  day  before,  and  what  they  were  the  next  day.  First 
remove  the  predictions  from  the  map.  After  the  predictions  have  been 
written  down,  show  the  actual  maps.  This  practice  may  be  continued 
until  the  class  becomes  fairly  proficient  in  predictions.  Toward  the  end 
of  these  exercises  have  the  students  sketch  their  predictions  on  outline 
maps ;  that  is,  upon  the  basis  of  their  study  of  a  map  for  a  given  day,  let 
them  make  a  weather  map  of  the  previous  and  succeeding  days.  Care 
should  be  taken  to  select  well-defined  storms  that  move  regularly,  other- 
wise the  results  maybe  poor.  (7)  Give  out  problems;  many  will  be 
suggested  by  a  study  of  a  series  of  weather  maps.  For  example,  given 
a  well-defined  low  at  Chicago,  temperature  34.5° :  is  it  clear  or  rainy  ? 
Is  the  temperature  probably  higher  or  lower  at  Minneapolis  ?  At  In- 
dianapolis? On  a  sketch  map  of  United  States  indicate  the  area  of 
probable  snow.  Of  rain.  What  will  the  weather  probably  be  next  day 
at  Chicago?  At  Cleveland?  (8)  Upon  the  basis  of  observations  with 
instruments  in  the  school  make  weather  predictions.  (9)  Each  day  give 
the  weather  map  to  one  of  the  students,  and  let  him  report  the  facts  of 
barometer,  temperature,  position  of  highs  and  lows,  etc. ;  or,  better, 
sketoh  them  on  an  outline  map  for  the  class  to  see.  Then  call  for 
predictions  from  the  class,  and  have  them  give  their  reasons.  Then 
read  the  prediction  on  the  map.  Next  day  call  for  a  statement  of  how 
nearly  correct  the  prediction  was. 


•appendix   I.     MAPS. 

Various  methods  are  employed  to  represent  the  surface  of  the 
earth  by  maps.  Among  these  are  relief  maps,  hachure  maps,  and 
contour  maps,  all  of  much  value  in  a  study  of  physical  geography. 

1.  Relief  Maps  or  Models.  —  Ordinary  maps  are  flat ;  and  the 
usual  political  map  makes  little  attempt  to  represent  relief.  Yet 
by  shading,  or  by  color,  some  are  made  to  indicate  the  general 
distribution  of  highlands  and  lowlands.  A  far  better  means  of 
representing  a  country  is  by  relief  map,  or  model,  in  which  the 
surface  is  actually  raised  to  represent  irregularities  of  the  land. 

Owing  to  the  small  size  of  such  maps,  it  is  usually  necessary  to 
exaggerate  the  vertical,  that  is,  make  the  scale  of  elevation,  or 
vertical  scale,  different  from  the  horizontal  scale.  Thus  one  inch 
vertically  may  represent  1000  feet,  while  in  the  horizontal  scale 
an  inch  represents  10,000  or  even  20,000  feet.  To  avoid  wrong 
impressions  from  the  use  of  such  maps,  care  should  be  used  to 
understand  and  make  allowance  for  this  exaggeration. 

The  great  expense  of  making  relief  maps  prevents  their  use  in 
most  school  laboratories.  Figures  22-26,  114,  460,  461,  464,  476, 
477,  and  485  are  photographs  of  such  models. 

2.  Hachure  Maps.  —  The  United  States  Coast  Survey  and  the  sur- 
veys of  many  European  countries  make  use  of  hachures  to  represent 
irregularities  of  the  surface  of  small  sections.  A  hachure  map  is 
one  in  which  the  relief  is  brought  out  by  shading,  through  the  use 
of  lines  drawn  more  or  less  closely  together,  and  all  pointing  in 
the  direction  of  the  slope  (Fig.  562).  Such  a  map  is  very  graphic, 
and  exceedingly  useful  in  a  study  of  the  general  form  of  the  land. 
For  some  purposes  its  usefulness  is  lessened  by  the  fact  that, 
though  it  clearly  brings  out  differences  in  elevation  between 
adjoining  regions,  it  does  not  tell  the  actual  elevations. 

3.  Contour  Maps.  —  The  fact  last  mentioned  has  led  other  sur- 
veys, for  example  the  U.  S.  Geological  Survey,  to  adopt  mntour 
lineSy  Qx  lines  passing  through  places  of  equal  elevation. 

428 


MAPS.  429 

Imagine  a  rather  irregular  beach  at  low  tide  when  there  are  no 
waves.  The  water  marks  a  contour  line,  and  extends  up  the 
depressions,  or  valleys,  in  the  sand.  This  may  be  called  the  0 
contour ;  if  the  tide  rises  five  feet,  a  new  contour  is  marked  five 
feet  above  the  other.     This  might  be  called  the  five-foot  contour. 

In  making  contour  maps,  sea  level  is  reckoned  as  0,  and  each 
contour  passes  through  all  places  on  the  map  that  are  at  the  same 
level  above  sea;  that  is,  places  which,  the  sea  would  touch  if  it 
rose  that  high.  Every  place  through  which  the  100-foot  contour 
passes  is  just  100  feet  above  sea  level.  On  such  maps,  therefore, 
it  is  possible  to  tell  the  elevation  of  every  place.  Contour  maps 
do  not  express  relief  so  graphically  as  hachure  maps,  but,  with  a 
little  study,  one  learns  to  quickly  interpret  from  them  the  forms  of 
the  land.  Plains  have  few  contours,  far  apart ;  gorges  have  many, 
close  together ;  rounded  hills  have  contours  of  different  shape  from 
those  on  steep-sided  hills,  etc.  Figures  78,  82,  121, 131, 137, 145, 
192,  and  193  are  contour  maps. 

On  the  U.  S.  Geological  Survey  maps  the  horizontal  scale  is 
usually  about  one  inch  to  the  mile.  The  vertical  scale,  or  contour 
interval,  is  usually  20  feet ;  that  is,  a  contour  is  drawn  for  every 
20  feet  pf  elevation.  Therefore,  the  vertical  distance,  or  interval, 
between  two  contours  is  20  feet.  In  sparsely  settled  or  moun- 
tainous regions  a  contour  interval  of  100  feet  is  often  chosen. 

Suggestions.  —  (1)  Find  out  if  the  U.  S.  Geological  Survey  (Wash- 
ingtoD,  D.C.)  has  issued  a  contour  map  of  your  vicinity.  If  so,  get  a  copy 
(cost  5  cents),  mount  it  (p.  437),  and  carry  it  on  your  walks  or  bicycle 
rides.  You  will  find  it  of  great  service.  (2)  Let  the  class  have  practice 
in  making  simple  contour  sketches;  for  example,  have  them  make  con- 
tours to  show  a  round  hill,  a  long  hill,  a  hill  steep  on  one  end,  two  hills 
and  a  valley,  a  broad  valley,  a  gorge,  etc.  Also  draw  simple  contour 
sketches  on  the  board  (for  example,  a  round  hill),  and  have  the  class 
make  cross  sections  of  them  ;  that  is,  sections  to  show  the  profile  as  if  the 
hill  were  sliced  through.  Keep  the  class  at  this  work  until  they  under- 
stand how  to  do  quickly  what  is  given.  (3)  From  some  model  select  a 
section,  and  have  the  class  sketch  a  contour  map  of  it.  (4)  Obtain  a 
series  of  contour  maps,  and  have  the  class  make  cross  sections  along 
lines  drawn  on  the  map  by  the  teacher.  To  make  these  sections,  first 
draw  a  line  on  the  paper  equal  in  length  to  the  line  on  the  map.  Then, 
for  the  vertical  scale,  draw,  parallel  to  this,  other  lines  ^^  inch  apart, 


430  NEW  PHYSICAL   GEOGRAPHY. 

Let  the  distance  between  two  of  these  lines  represent  20  feet.      Then 
proceed  to  draw  the  profile.     (5)  After  some  practice  in  cross-sectioning, 
select  a  series  of  maps  and  assign  to  each  student  part  or  all  of  a  map 
to  define  the  topography  in  words.     This  may  well  be  followed  by  other 
maps.     (0)   The  teacher  may,  possibly,  deem  it  worth  while  to  have  the 
class  make  a  map  of  a  small  area.     With  a  tape  line,  an  aneroid  barom- 
eter, a  level,  and  a  compass,  a  rough  map  may  easily  be  made.     (7)  If  the 
teacher  would  each  year  have  a  model  made  by  the  class,  the  school  would 
soon  accumulate  a  valuable  equipment.     It  is  not  very  difficult  to  make 
a  model.     For  the  first  one  start  with  a  simple  region  —  say  the  Marion, 
Iowa,  sheet.     Find  the  lowest  contour  on  the  sheet  and  transfer  it  to 
tracing  paper,  then  to  a  thin  cardboard  sheet  the  size  of  the  map.     Then 
cut  the  cardboard  along  the  line.     Tack  it  to  a  board,  or  thick  cardboard, 
the  size  of  the  map.     Do  the  same  for  the  next  highest  contour,  and  tack 
this  to  the  first.      Continue  until  there  is  a  pile  of  cardboards,  one  foj 
each  contour.     Divided  among  many,  this  is  not  a  very  difficult  task. 
With  molding  wax,  smooth  the  surface  so  that  no  cardboard  edges  ap- 
pear.    After  one  or  two  trials  a  very  satisfactory  model  will  be  made- 
On  more  complex  sheets  it  is  not  necessary  to  trace  every  contour.     An 
interesting  model  may  be  made  by  starting  with  a  large  number  of  sheets 
of  the  same  map  and,  instead  of  tracing  the  contours,  cut  the  map  itself, 
and  paste  sheet  on  sheet  until  each  contour  is  represented.     To  cut  the 
sheets  with  an  even  edge,  lay  the  map  on  a  sheet  of  glass  or  zinc  and  cut 
it  with  a  sharp  knife. 

Reference  Book.  —  Gannett,  Manual  of  Topographic  Methods,  Mono- 
graph XXIV,  U.  S.  Geological  Survey,  Washington,  D.C.,  1893,  $1.00. 


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APPENDIX   J,     LABORATORY   EQUIPMENT. 

1.  Models.  — £:.  E.  howell  (612  17th  St.,  N.AV.,  Washington,  D.C.) 
has  a  number  of  models  of  great  value  in  laboratory  work.  He  also 
offers  for  sale  large  photographs  of  these.  Catalogue  sent  on  applica- 
tion. G.  C.  Curtis  (64  Crawford  St.,  Boston,  Mass.)  has  a  set  of  three 
excellent  geographical  models  {glaciers,  volcanoes,  and  seacoast).  The  Har- 
vard Geographical  Models,  a  set  of  three,  are  sold  by  Ginn  &  Co.,  Boston, 
for  ^20  a  set.  These  last  two  sets  should  be  in  every  laboratory  of 
physical  geography.  The  Jones  model  of  the  earth  is  very  valuable  (cost 
$50,  A.  H.  Andrews  &  Co.,  Chicago).  For  construction  of  models 
from  topographic  maps,  see  page  430. 

2.  Maps.  —  The  Kiepert  and  the  Habenicht  Sf  Si/dow  relief  maps  of  conti- 
nents and  parts  of  Europe  are  the  best  maps  of  this  nature.  The  various 
government  bureaus  (see  below)  will  on  application  send  catalogues  of 
their  maps,  from  which  the  teacher  may  select  those  desired.  The  fol- 
lowing lists  have  been  carefully  prepared  to  secure  representative  maps 
of  various  phenomena,  and  they  may  serve  as  the  nucleus  of  a  map  col- 
lection for  laboratory  use.  For  further  suggestions,  see  pamphlet  by 
Davis,  King,  and  Collie,  I'he  Use  of  Governmental  Maps  in  Schools 
(Henry  Holt  &  Co.,  New  York,  1894,  $0.30)  ;  also  Davis,  Journal  of 
Geology,  Vol.  IV,  1896,  p.  484.  Foreign  maps  may  be  imported  through 
G.  E.  Stechert  (9  East  16th  St.,  New  York). 

The  entire  United  States  coast  is  charted  by  the  U.  S.  Coast  Survey, 
and  many  parts  of  the  country  are  mapped  by  the  U.  S.  Geological  Sur- 
vey. All  of  New  Jersey,  Massachusetts,  Connecticut,  Rhode  Island,  and 
most  of  New  Y'ork  are  now  mapped,  as  well  as  portions  of  each  of  the 
other  states.  The  Geological  Survey  topographic  sheets  may  be  ordered 
for  $0.05  each,  or  at  the  rate  of  $0.02  a  sheet  if  100  or  more  are  ordered. 
Money  must  be  sent  by  money  order  in  advance.  The  Geological  Sur- 
vey also  issues  special  maps,  for  example  a  series  of  different  scale  maps 
of  United  States;  also  geological  folios,  — perhaps  of  your  district. 

Each  school  should  have  sets  of  the  United  States  Geological  Survey 
Physiographic  Folios,  especially  the  first  two.  They  contain  selected 
maps,  with  description,  to  illustrate  physiographic  types.  Folios  1  and 
2  cost  $0.25  each ;  No.  3,  $0.50. 

4Sil 


432  NEW  PHYSICAL   GEOGRAPHY. 

3.  Use  of  Topographic  Maps.  —  The  use  made  of  topographic  sheets 
will  vary  with  the  teacher,  the  time  available,  and  the  number  and 
variety  of  sheets  at  hand.  The  following  is  the  method  adopted  by  one 
teacher,  who  has  all  the  maps  he  needs,  both  American  and  foreign. 
After  the  students  become  familiar  with  the  meaning  and  use  of  topo- 
graphic maps  (p.  429),  a  topic  is  chosen  for  a  laboratory  period,  say 
glacial  action,  or  one  phase  of  it,  and  typical  maps  (coijibined  sheets) 
illustrating  the  phenomena  are  hung  about  the  room  to  be  studied  and 
interpreted,  careful  notes  being  taken.  At  the  close  of  the  period  a 
review  quiz  is  held  by  the  teacher,  with  the  object  of  correlating  obser- 
vations and  bringing  out  points  whose  full  significance  may  not  have 
been  apparent  to  the  students.  The  lesson  is  definitely  correlated  with 
the  text-book  work,  and  generally  covers  a  topic  then  being  studied. 

In  addition  to  the  wall  maps,  single  sheets  are  placed  in  the  hands  of 
each  student,  each  sheet  clearly  illustrating  some  one  phase  of  the  topic 
chosen.  This  illustration  the  student  must  discover  by  observation. 
The  study  proceeds  somewhat  as  follows  :  (1)  Location :  (a)  latitude ; 
(h)  longitude  ;  (c)  position  on  United  States  contour  map ;  (d)  physio- 
graphic relationships  (i.e.  on  coastal  plain,  in  Adirondacks,  etc.).  (2) 
General  physiography :  (a)  highest  elevation  ;  (h)  lowest  section ;  (c)  direc- 
tion of  rivers  ;  {d)  abundance  or  scarcity  of  tributaries  ;  (e)  humid  or  arid 
region;  (/)  form  of  valleys;  (^r)  slopes;  (h)  nature  of  divides;  (i) 
direction  of  roads;  (y)  influence  of  physiography  on  roads,  railways, 
and  settlement.  (3)  Spec ijic  points  (for  example,  on  Elmira,  N.Y.,  sheet); 
(a)  find  morainic  hills  near  Lower  Pine  Valley  —  the  ice  front  stood 
there;  (b)  describe  J;he  valley  south  to  Elmira  and  southwest  to  East 
Corning  ;  (c)  measure  its  width  and  compare  with  that  occupied  by  the 
Chemung  River  west  of  Elmira;  (d)  what  is  a  wash  plain  (see  text- 
book) ?  (e)  could  this  be  a  wash  plain  ?  If  so,  what  change  has  it 
caused  in  the  depth  of  the  valley?  Would  it  account  for  the  broad,  flat- 
bottomed  valley  followed  by  the  railroad?  Might  it  have  raised  the 
valley  bottom  so  high  that  the  Chemung  could  not  follow  its  former 
course  via  Ilorseheads  ?     This  is  what  has  happened. 

The  subject  can  be  developed  formally  by  mimeographing  questions, 
or  putting  them  on  the  blackboard;  or,  better,  if  the  class  is  not  too 
large,  by  giving  general  directions,  then  asking  specific  questions,  either 
of  the  class  as  a  whole  or  of  individuals.  Work  done  on  individual 
sheets  is  included  in  the  review  at  the  end  of  the  exercise. 

By  the  above  method,  when  plains  are  studied  laboratory  exercises 
may  accompany  the  recitation  work ;  the  same  with  shore  lines,  lakes, 
mountains,  etc.  The  student  should  not  be  allowed  to  be  diverted  by 
other  phenomena  than  those  directly  beaming  on  the  topic.     The  same 


LABORATORY  EQUIPMENT.  433 

map  may  often  be  used  in  several  periods  to  illustrate  different  phe- 
nomena. In  this  work  the  student  is  expected  to  look  for  comparisons 
and  contrasts;  for  example,  under  "Plains,"  compare  and  contrast  the 
the  Fargo,  N.D.,  Kaibab,  Ariz.,  and  Palmyra,  N.Y.,  sheets. 

Another  method  used  is  to  stady  a  sheet  to  detect  all  phenomena 
represented  ;  but  this  lacks  many  of  the  advantages  of  a  study  by  topics. 
In  the  absence  of  a  regular  laboratory  manual,  it  is  necessary  for 
teachers  to  develop  their  own  methods,  and  this  Appendix  is  merely  a 
hint  as  to  one  direction  in  which  this  may  be  done.  It  calls  for  sacrifice 
of  time  and  energy  on  the  part  of  the  teacher ;  but  all  who  are  willing  to 
make  this  sacrifice  will  be  abundantly  repaid  by  the  improved  work  and 
greater  interest  of  the  class.  Even  if  formal  laboratory  work  is  not  given, 
the  maps  are  of  great  use  as  illustrations  of  the  text. 

4.  One  Hundred  Selected  Sheets,  United  States  Geological  Survey,  Topo- 
graphic Map.  —  These  maps  should  be  purchased  by  the  hundred  (-12  a 
hundred) ;  and  it  is  desirable  to  provide  enough  sets  for  each  student 
in  the  laboratory  to  have  a  copy  of  each,  or',  at  least,  to  provide  one  for 
every  two  students.     They  should  be  mounted  (p.  437). 

(1)  Glassboro,  N.J. ;  (2)  Leonardtown,  Md. ;  (3)  Pt.  Lookout,  ALL; 
(4)  Fargo,  N.D.;  (5)  Hamlin,  N.Y.;  (6)  Marion,  Iowa:  (7)  Wichita, 
Kan.;  (8)  Butler,  Mo.;  (9)  Marshall,  Ark.;  (10)  Lamar,  Colo.; 
(liyBrowmvood,  Tex.;  (12)  Coleman,  Tex.;  (13)  Higbee,  Colo.;  (14)  Kai- 
bab, Ariz.:  (15)  Watrous,  N.M.;  (16)  Boise,  Idaho;  (17)  Modoc 
Lava  Bed,  Cal. ;  (18)  Elmira,  N.Y.;  (19)  Kaaterskill,  N.Y.;  (20)  Gaines, 
Pa.;  (21)  Briceville,  Tenn. ;  (22)  Scottsboro,  Ala.;  (23)  Salyersville, 
Ky.;  (24)  Huntington,  W.Va. ;  (25)  Pikeville,  Tenn.;  (26)  Bisuka, 
Idaho;  (27)  Great  Falls,  Mont.;  (28)  St.  Paul,  Mitm. ;  (29)  Palo 
Pinto,  Tex.;  (30)  Delaware  Water  Gap,  Pa.;  (31)  West  Point,  N.Y.; 
(32)  Jefferson  City,  Mo. ;  (33)  Junction  City,  Kan. ;  (34)  Kearney, 
Neb.;  (35)  Lexington,  Neb.;  (36)  Donaldsonville,  La.;  (37)  Point  a  la 
Hache,  La.;  (38)  Cohoes,  N.Y.;  (39)  Springfield,  Mass.;  (40)  Alturas, 
Cal.;  (41)  Pikes  Peak,  Colo.;  (42)  Telluride,  Colo.;  (43)  Platte  Can- 
yon, Colo.;  (44)  Huerfano  Park,  Colo.;  (45)  Livingston,  Mont.;  (46)  Mt. 
Washington,  N.H.;  (47)  Becket,  Mass.;  (48)  Monadnock,  N.H.; 
(49)  Hartford,  Conn.;  (50)  Mt.  Marcy,  N.Y.;  (51)  Monterey,  Va.; 
(52)  Fort  Payne,  Ala.;  (53)  Estillville,  Ky.;  (54)  Franklin,  W.Va.; 
(55)  Maynardville,  Tenn.;  (56)  Hazleton,  Pa.;  (57)  Lykens,  Pa.; 
(58)  Atlanta,  Ga.  ;  (59)  Lassen  Peak,  Cal;  (60)  Shasta,  Cal.;  (61)  Mt. 
Taylor,  N.M.;  (62)  Marysville,  Cal.;  (63)  Ashland,  Ore.;  (64)  Henry 
Mountains,  Utah;  (65)  Sierraville,  Cal.;  (66)  Disaster,  Nev. ;  (67)  Para- 
dise, Nev.;  (68)  Granite  Range,  Nev.;  (69)  Tooele  Valley,  Utah;  (70)  Salt 
Lake,    Utah;  (71)   Boothbay,  Me.;   (72)   Coos  Bay,   Ore.;   (73)    Seattle, 

2f 


434  NEW  PHYSICAL   GEOGRAPHY, 

Wash.;  (74)  San  Francisco,  Cat. ;  (75)  New  Haven,  Conn.;  (76)  Brook- 
li/n,  N.Y.;  (77)  Charlestown,  R.I.;  (78)  New  London,  Conn.; 
(79)  Duluth,  Minn.;  (80)  Pulaski,  NY. ;  (81)  Marthas  Vineyard, 
Mass.;  (82)  Atlantic  City,  N.J.;  (83)  Barnegat,  N.J.;  (84)  Sandy 
Hook,  N.J.;  (85)  Boston  Bay,  Mass.;  (86)  Mt.  Lyell,  Cal.; 
(87)  Minneapolis,  Minn.;  (88)  Plymouth,  Mass.;  (89)  Stonington,  Conn.; 
(90)  Bal'/winsi'ille,N.Y.;  (91)  Newcomb,  NY. ;  (92)  Elizabethtown,  NY. ; 
(93)  Plaltsburg,  NY.;  (94)  Skaneateles,  NY.;  (95)  Ot'iW,  iV^.F.;  (96) 
iacon,  //^.;  (97)  Ottawa,  III.;  (98)  Watertown,  Wis.;  (99)  TFee^/s- 
j9or?,  iV.F.;  (100)   Os?oe^o,  iV.F. 

The  following  must  be  ordered  as  Special  Sheets:  (A)  Norfolk  Special, 
$0.10;  (B)  New  York  City  and  Vicinity  Special,  $0.25;  (C)  Rochester 
Special,  ^O.IO ;  (D)  Niagara  River  and  Vicinity  Special,  $0.10;  (E)  St. 
Louis  and  Vicinity  Special,  $0.10 ;  (F)   Crater  Lake  Special,  $0.05. 

The  following  classified  list  calls  attention  to  some  of  the  principal 
features  illustrated  on  the  above  maps.     The  teacher  will  find  others. 

Coastal  Plain,  1-3,  82,  83,  A;  Lake  Plains  (West),  59,  65-70;  Lake 
Plains  (Lake  Agassiz),  4;  Lake  Plains  (Ontario),  5,  C,  D ;  Lava  Plains 
(Plateaus,  West),  16,  17,  26,  61;  Central  Plains,  6,  8,  32,  96,  97;  Great 
Plains  (more  or  less  dissected),  7,  10,  12,  27,  29,  33,  35;  Dissected  Arid 
Plateau,  13,  14,  15,  61;  Escarpments,  14,  D;  Mesas,  11,  13,  14,  15,  61; 
Buttes,  12,  13,  26;  Desert,  66-70;  Desert  Sand  Dunes,  66,  67;  Dissected 
Moist  Plateaus,  9,  18,  23,  25,  94,  95;  Catskills,  19  ;  Immature  Drainage,  1, 
83,  A  ;  Post-glacial  Young  Streams,  28,  38,  94,  95,  96,  C,  D  ;  Young  Valleys, 
9,  13,  26,  27,"  49;  Waterfalls,  27,  C,  D;  Canyons,  13,  14,  16,  20;  Mountain 
Gorges,  43,  45;  Water  Gaps,  30,  31,  51,  52,  57;  Mature  Valleys,  18-24, 
38,  39,  47-58,  75,  94,  95;  Arid  Land  Drainage,  13-16,  40,  65-70;  Allu- 
vial Fans,  45,  65 ;  River-made  Plains,  60,  62  ;  Braided  Course,  34,  35,  66  ; 
Floodplains,  8,  9,  32,  34,  35,  87,  96,  97,  E  ;  Bluffs,  32,  35,  E  ;  Levee,  36 ; 
Crevasse,  36 ;  Oleanders,  8,  32,  33,  52,  53,  55,  E ;  Intrenched  Meanders,  23, 
29  ;  Delta,  93  ;  Terraces,  38,  39,  49,  96  ;  Erie  Canal,  99  ;  Irrigation,  10,  70 ; 
Basin  Ranges,  40;  Coast  Ranges,  60,  72,  74;  Sierra  Nevada,  65;  Rocky 
Mountai?is,  4:1-45;  Appalachians,  2\,  25,  30,  51-57;  Adlrondacks,  50,  91, 
92  ;  New  England  Mountains,  46-49,  75,  77 ;  Piedmont,  58  ;  Young  Moun- 
tains, 40-45,  60,  65,72,  74;  Mountains  (early  maturity),  46  ;  Mature  Moun- 
tains, 30,  31,39,  47,  57,  71,  75,  77,  78,  89,  91-93  ;  Mountain  Ridges,  51-57  ; 
Old  Mountains,  58,  85  ;  Peneplain,  58 ;  Monadnocks,  48,  58 ;  Volcanoes^  59- 
62,  F ;  Laccolites,  64 ;  Trap  Ridges,  39,  75  ;  Palisades,  B ;  Glaciers,  60 ; 
Cirques,  86;  Moraines,  76, 77,  81,  87-89 ;  Wash  Plains,  18, 76, 77,  81 ;  iMoraine 
Kettles,  88;  Karnes  (Pinnacle  Hills),  C;  Drumlins,  49,  85,  90,  98-100; 
Glacial  Lake  Overflow  Channels,  90,  96,  97,  99  ;  Lake  on  Coastal  Plain,  A  ; 
Delta  Lakes,  37 ;  Ox-bow  Lakes,  8,  33,  E  ;   Volcanic  LakeSy  59  ;  Crater  Lakes, 


LABORATORY  EQUIPMENT.  435 

59,  63,  F;  Glacial  Lakes  and  Swamps,  31,  45,  47,  48,  50,  77,  78,  85-94,  98^ 
100;  Lake  Champlain,  93;  Finger  Lakes,  94,  95;  Coastal  Plain  Swamps,  1, 
A;  River  Swamps,  1,  62,  87,  96,  A;  Delta  Swa7nps,  36,  37;  Lake  Swamps, 
80,  93, 100,  C  ;  Alkali  Flats  and  Plat/as,  65,  66,  68;  Drowned  Coastal  Plain, 
2,  3,  83,  84,  A;  Drowned  Coast,  71-78,  81,  85,  89,  B;  Drowned  Lake 
Coast,  79,  80,  93,  100,  C ;  Harbors,  73-75,  78,  79,  A,  B;  Wave-cut  Cliffs, 
84,  100;  Wave-cut  Islands,  ^^;  Beaches,  72;  Tied  Islands,  So;  Bars, 
shutting  in  Bays,  77,  79-81,  85,  100,  C;  Sa?id  Bars,  76,  78,  81,  88,  89; 
Hooks,  84;  Sand  Dunes,  72,  83,  84;  Offshore  Bars,  inclosing  Lagoons,  82- 
84,  A ;  Salt  Marshes,  74-76,  78,  82,  85,  89,  A,  B. 

5.  Thirty -five  Grouped  Sheets.  —  The  following  groups  of  sheets  a  '« 
selected  for  mounting  to  make  large  maps  (see  directions  below).  Each 
group  illustrates  well  at  least  one  phenomenon,  and  a  number  illustrate 
several.  In  addition,  they  all  contain  many  important  details  worthy  of 
study.  It  would  also  be  desirable  to  secure  and  mount  in  a  large  map  all 
the  sheets  in  the  vicinity  of  the  home  region.  Nearly  all  of  these  sheets 
could  be  used  singly  if  mounting  in  groups  seems  too  difficult. 

1.  Colorado  River  and  Vicinity  —  illustrating  plateaus,  mesas, 
buttes,  canyons,  volcanoes,  arid  drainage,  the  following  sheets :  (Pioche,  St. 
George,  Kanah,  Escalante,  Henry  Mountains,  Utah,  Marsh  Pass,  Echo  Cliffs, 
Kaibah,  Mt.  Trumbull,  St.  2'homas,  Camp  Mohave,  Diamond  Creek,  Chino, 
San  Francisco  Mt.,  Tusayan,  Ariz.).  2.  Overburdened  Platte  River 
—  also  great  plains  (^Kearney,  Wood  River,  Grand  Island,  Neb.).  3. 
Same  —  (Minden,  Kenesaw,  Neb,).  4.  Connecticut  Valley — bor- 
dering upland,  lowland,  trap  ridges,  terraces,  ox-bow  lake  {Cireenfield, 
Warwick,  Northampton,  Bel'chertown,  Springfeld,  Palmer,  Mass.).  5.  River 
Floodplain  and  Meanders  —  also  great  plains  {Kansas  City,  Oska- 
loosa,  Olathe,  Lawrence,  Kan.).  6.  Mississippi  Delta  (West  Delta,  East 
Delta,  La.).  T  Mississippi  Delta  and  Floodplain  —  also  location  of 
New  Orleans  (Boro,cCt  Carre,  Spanish  Fort,  Chef  Menteur,  Rigolets,  Toulme, 
Bodreau,  Shell  Beach,  St.  Bernard,  New  Orleans,  Hahnville,  La  For' 
tuna,  Deine,  Point  a  la  Hach'',  Barataria,  Cut  Off,  Forts,  Quarantine,  Ft. 
Livingston,  Creole,  Lake  Felicity,  La.).  8.  Alluvial  Fans  —  arid  region 
{Pomona,  Cucamonga,  San  Bernardino,  Cal.).  9. ,  Coastal  Plain  — 
also  shore  lines,  bars,  marsh,  etc.  {Boi-deniown,  Cassville,  Asbury  Park, 
Pemberton,  Whiting,  Barnegat,  N.J.).  10.  Coastal  Plain  —  drowned, 
swampy  {Prince  Frederick,  Brandywine,  Wicomico,  Leonardtoicn,  Md.). 
11.  Coastal  Plain — young  drainage,  lakes,  and  swamps  {WiUiston, 
Citra,  Dunnellon,  Ocala  Isala,  Aparka,  Pana  Soffkee,  Fla.).  12.  Lake 
Plain  —  bed  of  Lake  Agassiz  {Fargo,  Casselton,  N.D.).  13.  Great 
Plains  {Wichita,  Cheney,  Kingman,  Wellington,  Caldwell,  Anthony,  Kan.). 
14.  Maturely  Dissected  Plateau  {Salyersville,  Prestonsburg,  Hazard^ 


436  NEW    PHYSICAL   GEOGRAPHY. 

Whiteshurg,  Ky.).  15.  Same  (Huntington,  Charleston,  Kanawha  FaUs, 
Warjiehl,  Oceana,  Raleigh,  W.Va.)-  16.  Mature  Mountains  and  Pla- 
teau (Chattanooga,  Sewanee,  Ringgols,  Stevenson,  Tenn.) .  17.  Dissected 
Arid  Land  Plateau  —  canyons,  mesas,  buttes,  etc.  {Higbee,  Timpas, 
Apishapa,  Mt.  Carrizo,  Mesa  de  Maya,  El  Moro,  Colo.).  18.  Mesas. 
Buttes,  Volcanoes,  Arid   Drainage    (Wingate,   Mt.   Taylor,   N.M.). 

19.  Appalachian  Ridges  —  Susquehanna,  water  gaps,  broacl  valleys,  etc. 
(Sunhury,  Shamokin,  Millershurg,  Lykens,  Harrishurg,  Hummelstown,  Pa.). 

20.  Southern  Appalacheans  (Greenville,  Roan  Mt.,  Ashville,  Mt.  Mitch- 
ell, N.C).  21.  Southern  Appalachians  (Staunton,  Monterey,  Hunters- 
villCf  Lexington,  Natural  Bridge,  Lewishurg,  Va.,  W.Va.).  22.  Mountain 
Ridges  —  river  meanders,  Shenandoah  valley  (Harper's  Ferry,  Winchester, 
Romney,  Warrenton,  Luray,  Woodstock,  Va.).  2.3.  New  England  Moun- 
tains—  even-topped  upland,  Monadnock  (Peterhoro,  Monadnock,  Keene, 
N.H.,  Fitchhurg,  Winchendon,  Warwick,  Mass.).  24.  Adirondack^  — 
part  of  Lake  Champlain,  glacial  lakes  (Lake  Placid,  Ausahle,  Willshoto, 
Mt.  Marcy,  Elizahethtown,  Port  Henry,  Schroon  Lake,  Paradox  ^ ake,  Ticon- 
deroga,  N.Y.).  2.5.  Appalachians  and  Virginia  PiedmoinT  (Gooch- 
land, Palmyra,  Buckingham,  Amelia,  Farmville,  Appomattox,  Va.).  26. 
Piedmont  and  Coastal  Plain  —  location  of  Philadelphia  (Germantown, 
Norristown,  Chester,  Philadelphia,  Pa.).  27.  Drumlins  —  glacial  lakes, 
cities  on  river  with  rapids  due  to  glacial  action,  also  beaches  and  salt 
marshes  (Haverhill,  Newhuryport,  Lawrence,  Salem,  Mass.).  28.  Finger 
Lakes  —  mature  plateau,  post-glacial  gorges,  lake  deltas  (Geneva,  Auburn, 
Skaneateles,  Ovid,  Genoa,  Moravia,  Watkins,  Ithaca,  Dryden,  N.Y.). 
29.  Drumlins  —  drainage  interfered  with  by  drift,  overflow  channels, 
lake  shores  (Oswego,  Sodus  Bay,  Pultneyville,  Weedsport,  Clyde,  Palmyra, 
Auburn,  Geneva,  Phelps,  N.Y.).  30.  Drumlins — glacial  lakes  and 
swamps' (il/arfjson,  5wn  Prairie,  Waterloo,  Watertown,  Evansville,  Stoughton, 
Koshkonong,  Whitewater,  Wis.).  31.  Drowned  Coast  (Gardiner,  Wis- 
casset,  Boothbay,  Bath,  Me.).  32.  Same  (Boothbay,  Bath,  Freeport,  Gray, 
Small  Point,  Casco  Bay,  Portland,  Me.).  33.  Bays,  —  bars,  wave-cut 
cliffs,  moraine,  wash  plain  (Marthas  Vineyard,  Gay  Head,  Mass.).  34. 
Cape  Cod  —  bars,  wave-cut  cliffs,  sand  dunes,  moraine,  morainic  lakes 
(Provincetown,  Welljieet,  Chatham,  Yarmouth,  Barnstable,  Mass.).  35.  Yel- 
lowstone Park  (Gallatin,  Canyon,  Lake,  Shoshone,  Wy.). 

6.  Thirty  Selected  Sheets,  United  States  Coast  Survey,  illustrating  Typi- 
cal Coast  Lines.—  (Washington,  D.C.  |0.50  each;  catalogue  free;  order 
by  number.)  0  General  Chart,  coast  of  Maine  and  Massachusetts)', 
103,  104, 105,  106  (Maine  coast,  more  detailed)  ;  108  (Coast  from  southern 
Maine  to  Cape  Ann)  ;  109  (Boston  Bay)  ;  8  (Approaches  to  New  York, 
Gay  Head  to  Cape  Henlopen)  ;    113  (Narragansett  Bay)  ;    52  (Montauk 


LABORATORY  EQUIPMENT.  437 

Point  ^o  New  York,  with  Long  Island  Sound)  ;  119  (^Southern  shore  of  Long 
Island)  ;  121,  122,  123  (New  Jersey  coast,  Sandy  Hook  to  Cape  May)  ;  370 
{Delaware  and  Chesapeake  bays)  ;  11  (Cape  Hatteras  to  Cape  Romain)  ; 
142  (Cape  Hatteras)  ;  147  (Cape  Lookout)  ;  15  (Straits  of  Florida,  Coral 
Reefs)  ;  170  (Key  West  and  Vicinity,  Coral  Reefs)  ;  1007  (General  Chart, 
Gulf  of  Mexico)  ;  188  (Mobile  Bay)  ;  19  (Mississipjn  Delta  and  vicinity)  ; 
194  (Mississippi  Delta) ;  21  (Galveston  to  the  Rio  Grande)  ;  212  (Bar 
from  Rio  Grande  northward)',  5400,  5500  (California  coast);  3089,  8100 
(Drowned  ^^.askan  coast). 

7.  River  and  Lake  Maps.  —  The  Mississippi  River  Commission  (St.  Louis), 
and  the  Missouri  River  Commission  (St.  Louis)  issue  charts  of  these  rivers, 
of  which  the  following  are  especially  useful.  Alap  of  Alluvial  Valley  of 
Mississippi,  8  sheets  ($1  per  set)  ;  Upper  Mississippi,  4  sheets  ($0.70  per  set) ; 
Mississippi,  Charts  8,  22,  35,  36,  38,  39,  52  of  the  map  on  scale  of  1  :  20,000, 
showing  meanders,  oxbows,  etc.  ($0.26  per  sheet).  If  the  school  is  located 
on  the  river,  the  sheets  of  that  vicinity  should  be  secured. 

Charts  of  the  Great  Lakes  (United  States  Engineer's  Office,  Detroit, 
Mich.)  illustrate  many  shore-line  phenomena.  Nos.  1,  5,  6;  also  Lake 
Ontario,  Niagara  River,  Lake  Erie,  and  Lake  St.  Clair  are  especially  valu- 
able. If  the  school  is  on  the  lakes,  much  use  should  be  made  of  the  lake 
charts,  especially  those  near  by. 

8.  Mounting  Maps.  —  It  is  real  economy  to  have  all  maps  backed  with 
cloth.  This  will  be  done  by  many  bookbinders,  or  it  can  be  done  in  the 
dchool,  using  a  thin,  bleached,  white  cotton  cloth  of  ordinary  width  for 
«iingle  sheets  ;  extra  width  for  grouped  sheets.  Use  ordinary  flour  paste, 
which  costs  very  little  if  purchased  from  a  paper  hanger.  For  success- 
nil  map  mounting  have  a  smooth  surface  (a  large  drawing  board  or  table 
top)  on  which  to  tack  the  cloth.  Stretch  the  cloth  and  tack  it  firmly  on 
all  sides,  then  thoroughly  wet  it.  Apply  paste  to  the  back  of  the  map 
and  allow  it  to  lie  until  thoroughly  limp,  then  put  it  on  the  cloth,  which 
must  not  be  too  wet.  Carefully  press  the  map  to  the  cloth  with  a  piece 
of  clean  cloth  or  a  photographic  roller.  Leave  until  thoroughly  dry  (at 
least  24  hours). 

Combined  sheets  must  first  be  trimmed,  leaving  on  alternate  sheets  a, 
margin  of  ^  inch  for  adjoining  sheets  to  overlap.  For  trimming,  to  secur  ^, 
an  even  cut,  place  the  map  on  a  sheet  of  zinc  (tacked  to  a  board),  an%i, 
with  a  sharp  knife,  cut  along  a  metal  straightedge  placed  on  the  map. 
If  a  map  is  not  complete,  blank  spaces  may  be  filled  with  white  paper. 

Large  maps  should  be  rolled,  and  a  wood  turner  will  supply  rolk^-s  at 
small  cost ;  also  strips  for  the  top  of  the  map.  Curtain  rings  -nay  be 
screwed  into  the  wooden  strip  for  hanging  the  map,  which,  for  class  use, 
may  be  hung  to  brass  rods  (|  inch  in  diameter)  along  tlw?  uides  of  the 


438  NEW   PHYSICAL    GEOGRAPHY. 

room.  A  curtain  hanger  will  make  hooks  to  hang  over  the  rods.  If 
single  sheets  are  also  hung,  Dennison  gummed-cloth  suspension  rings 
may  be  used. 

Single  sheets  are  best  kept  in  a  case  of  shallow  drawers,  using  care  not 
to  put  too  many  in  a  drawer,  for  they  are  then  difficult  to  handle.  Rolled 
maps  are  best  preserved  when  kept  in  a  case  with  shallow  partitions, 
allowing  the  rolled  map  to  lie  horizontally.  A  cabinet-maker  will  build 
a  combnied  case  for  rolled  and  flat  maps. 

9.  Minerals  and  Rocks,  —j^.  E.  Howell,  612  17th  St.,  N.W.,  Washing- 
ton, and  Ward's  Natural  Science  Establishment,  Rochester,  N.Y.,  offer 
cheap  sets  of  minerals  and  rocks  suitable  for  laboratory  use  in  connec- 
tion with  Tarr's  Geology  or  Physical  Geography.  G.  B.  Frazer,  West 
Medford,  Mass.,  is  another  reliable  dealer. 

10.  Meteorological  Maps,  etc.  —  Application  should  be  made  to  have 
the  weather  map  sent  regularly  to  the  school ;  and  duplicates  of  out  of  date 
maps  may  possibly  be  secured  on  application.  Meteorological  instru- 
ments (see  p.  420)  may  be  purchased  of  J.  P.  Friez,  Baltimore,  Md.,  or 
//.  J.  Green,  Brooklyn,  N.Y. 

11.  Lantern  Slides.  —  Various  firms  now  supply  lanterns  for  schools, 
the  most  satisfactory  being  electric  lanterns.  A  set  of  lantern  slides, 
selected  by  Prof.  W.  M.  Davis,  is  sold  by  E.  E.  Howell  (address  above)  ; 
T.  H.  McAllister  (49  Nassau  St.,  New  York)  has  a  series  of  geographical 
slides,  and  H.  W.  Fairbanks  (Berkeley,  Cal.)  has  a  set  of  western  slides 
for  sale.  The  Geography  Supply  Bureau  (Ithaca,  N.Y.)  has  a  selected  set 
of  about  a  thousand  of  Professor  Tarr's  best  negatives  from  which  slides 
will  be  made  on  order.  These  slides  were  selected  with  the  advice  and 
assistance  of  Professor  Tarr,  and  with  special  reference  to  their  adapta^ 
tion  to  use  in  schools.  The  set  includes  practically  all  the  phenomena 
of  Physical  Geography.  A  printed  catalogue,  with  description  of  each 
slide  and  suggestions,  and  outline  questions  for  its  use,  will  be  sent  on 
application. 


APPENDIX   K.    FIELD  WORK. 

The  value  of  field  work  is  such  that  every  course  in  physical 
geography  ought  to  be  accompanied  by  at  least  some.  No  labora- 
tory or  text-book  work  can  take  the  place  of  well-conducted  field 
work ;  it  is  worth  undertaking  even  if  Saturday  is  the  only  time 
available  for  it.  But  a  progressive  school  should  provide  regular 
periods  for  out-of-door  v/ork. 

Directions  for  field  work  of  sufficient  explicitness  to  be  useful  as 
a  guide  cannot  be  given  without  taking  up  far  more  space  than  is 
available  in  this  book.  What  kind  of  work  to  give  is  a  question 
which  can  be  settled  only  by  local  conditions ;  therefore  the 
teacher  must  develop  his  own  outline.  There  is  no  region  with- 
out some  good  physiographic  phenomena  within  easy  reach. 

Properly  to  make  use  of  these  field  opportunities  demands  per- 
sonal knowledge  of  methods  on  the  part  of  the  teacher.  There  are, 
of  course,  many  teachers  of  physical  geography  who  have  not  had 
the  training  necessary  for  this  work ;  for  even  the  universities  have 
been  giving  regularly  organized  field  courses  only  in  the  past  few 
years.  Most  summer  schools  in  large  universities  offer  instruc- 
tion in  this  direction,  and  any  teacher  who  desires  to  give  field 
work,  but  lacks  the  necessary  training,  can  secure  it  easily  and  at 
slight  expense.  Knowing  how  field  work  is  conducted  in  one 
region,  any  real  teacher  can  adapt  the  same  methods  to  his  own 
needs. 

It  is  by  the  introduction  of  laboratory  work,  indoors  and  out, 
that  physical  geography  is  gaining  for  itself  a  rank  which  is 
placing  it  on  a  par  with  other  science  courses  in  the  secondary 
school  curriculum.  Ten  years  ago  scarcely  a  secondary  school  in 
the  country,  and  very  few  normal  schools  and  universities,  gave 
organized  laboratory  and  field  work  in  physical  geography.  Now 
many  of  the  better  secondary  schools  provide  for  it  and  have 
specially  equipped  laboratories.     The  normal  school  or  university 

439 


440  NEW  PHYSICAL   GEOGRAPHY, 

course  that  does  not  include  such  work  is  now  considered  weak 
and  unsatisfactory.  If  the  next  ten  years  witnesses  an  advance 
equal  to  that  of  the  last  ten,  the  same  will  be  true  of  physical 
geography  in  the  secondary  schools.  A  course  in  chemistry  and 
physics  that  is  solely  a  text-book  course  is  now  considered  ridicu- 
lous ;  the  same  should  be  true  of  physical  geography.  The  fact 
that  it  is  likely  to  be  so  considered  within  ten  years  should  spur 
on  every  teacher  of  the  subject  to  the  effort  to  prepare  himself 
for  the  work  and  provide  for  it.  The  task  is  not  a  great  one,  and 
the  reward  is  well  worth  the  effort. 

The  following  are  some  of  the  phenomena  that  are  likely  to  be  found 
within  easy  reach  of  a  school.  (1)  Illustrations  of  weathering:  cliffs, 
ledges,  bowlders,  old  stone  or  brick  buildings.  (2)  Nature  of  country 
rock:  in  river  valleys,  railway  cuts,  quarries.  In  such  places  stratifica- 
tion, joint  planes,  folding  and  faulting,  and  fossils  may  possibly  be 
found.  (3)  The  soil :  for  characteristics  and  depth,  look  in  cuts,  as  in 
(2).  Is  it  a  soil  of  rock  decay  or  transported?  If  the  former,  study  its 
origin  in  the  cut.  If  the  latter,  how  transported?  (4)  River  transport 
tation :  road  gutters,  plowed  fields,  small  wet-weather  streams,  —  nature 
of  work,  load  carried,  disposition  of  load,  result  of  removal.  Fine 
examples  of  young  stream  valleys,  alluvial  fans,  deltas,  and  waterfalls 
(over  pebbles)  are  very  often  found  in  a  road,  field,  or  railway  cut. 
(5)  River  loork  and  valley  formation :  source  of  water ;  variation  in 
volume;  sediment  load;  variation;  source  of  sediment;  temporary  dis- 
posal of  it,  —  on  stream  bed,  in  bars,  in  floodplains,  etc. ;  place  of  final 
deposit  of  sediment ;  effect  of  removal  of  sediment  on  valley  form.  The 
entire  subject  of  river  work  and  life  history  of  valleys  may  be  built  up 
around  one  or  two  field  excursions  to  a  near-by  stream.  It  is  not  neces- 
sary to  have  grand  waterfalls  or  broad  floodplains.  A  meadow  brook 
has  its  full  lesson.  (6)  Shore  lines :  a  lake  shore  or  the  sea  shore  ;  even 
a  river  bank  or  the  shore  of  a  pond  may  serve.  What  are  the  waves 
doing  ?  What  work  have  they  accomplished  ?  Why  are  the  pebbles  round  ? 
Where  has  the  ground-off  material  gone?  What  is  the  source  of  the  peb- 
bles or  sand  ?  Which  way  are  they  moving  ?  Are  there  bars,  wave-cut 
cliffs,  small  stream  deltas,  shore  swamps?  Perhaps  there  are  all,  possibly 
only  one;  in  the  latter  case  study  that,  even  though  it  may  seem  very 
insignificant.  (7)  Glacial  phenomena  :  strife;  till  banks,  —  in  railway  or 
other  cuts ;  nature  of  material ;  scratched  stones,  etc.  Are  the  pebbles 
or  bowlders  foreign,  i.e.  unlike  the  country  rock?  Is  the  till  unstrati- 
fied?  Why?  Find  cuts  of  stratified  drift  —  evidence  of  water  action. 
There  may  be  moraines,  kames,  eskers,  or  drumlins. 


FIELI>   WORK.  441 

Besides  these  there  may  be  plains,  or  moiu^^aias,  or  plateaus,  or  vol- 
canic phenomena.  If  so,  so  much  the  better -•  buvi  profitable  field  work 
does  not  necessarily  demand  grand  features.  It  will  be  well  to  have 
most  of  the  excursions  devoted  to  details  and  the  study  of  principles : 
hence  a  seemingly  small  illustration  may  be  of  the  very  highest  value. 
At  the  same  time,  the  field  work  should  not  entirely  ignore  the  broad, 
general  features.  A  very  profitable  excursion  may  be  conducted  in  a 
high  tower,  or  on  a  high  hill  overlooking  the  surrounding  country. 

Field  excursions  should  be  made  for  the  purpose  of  showing  the  rela- 
tionship between  physiographic  phenomena  and  human  interests.  They 
may  often  be  combined  with  the  other  excursion  suggested  above.  For 
example,  an  excursion  might  well  consider  the  reason  for  the  location  and 
the  nature  of  work  in  a  quarry ;  the  location  and  the  difficulties  in  the 
way  of  laying  a  railway,  i.e.  the  cuts,  tunnels,  etc..  necessary  ;  the  differ- 
ences in  the  soil  and  their  relation  to  plant  life,  and  especially  to  crops  ; 
the  location  of  mills,  etc.  Here  again  the  broad  influences  of  physio- 
graphic conditions  should  not  be  overlooked.  B^^  A\  means,  the  field 
work  should  show  clearly  the  significance  of  the  li^c^Mon  andld'?*^"^<)pment 
of  the  home  town  and  its  industries. 


APPENDIX  L.  REFERENCE  BOOKS. 

The  reference  books  listed  at  the  end  of  each  chapter  deal  hi  part,  if 
not  entirely,  with  the  topic  treated  in  that  chapter.  There  are  a  number 
of  general  books,  some  of  which  are  included  in  those  lists,  which  should 
be  in  every  physical  geography  laboratory.  Among  these  are  most  of 
the  following:  — 

Mill,  International  Geography,  Appleton  &  Co.,  N.Y.,  1902,  $3.50; 
Huxley,  P/ujsiographij,  Macmillan  Co.,  N.  Y.,  1891,  .|1.80 ;  Geikie,  Scenery 
of  Scotland,  Macmillan  Co.,  N.  Y.,  1901,  $3.25 ;  Tarr,  Physical  Geography  of 
New  York  State,  Macmillan  Co.,  N.Y.,  1902,  $3.50;  Lubbock  (Lord 
Avebury),  Scenery  of  England,  Macmillan  Co.,  N.  Y.,  1902,  $2.50 ;  National 
Geographic  Monographs,  Physiography  of  the  United  States,  American  Book 
Co.,  X.Y.,  1895,  $2.50;  Shaler,  Outline  of  the  Earth^s  History,  Appleton 
&  Co.,  N.  Y.,  1898,  $1.75;  Shaler,  Aspects  of  the  Earth,  Scribner's  Sons, 
N.Y.,  1890,  $2.50;  Geikie,  Fragments  of  Earth  Lore,  John  Bartholomew, 
Edinburgh,  1893,  12s.  Qd. ;  Bonney,  Story  of  Our  Planet,  Cassell,  London, 
1898,  7s.  M. ;  Geikie,  Earth  Sculpture,  Putnam's  Sons,  N.Y.,  1898,  $2.00 ; 
Marr,  The  Scientific  Study  of  Scenery,  Methuen  &  Co.,  London,  1900,  6s.; 
Salisbury,  Physical  Geography  of  New  Jersey,  Vol.  IV,  Final  Report, 
New  Jersey  Geological  Survey,  Trenton,  1902  ;  Dryer,  Studies  in  Indiana 
Geography.  Inland  Printing  Co.,  Terre  Haute,  Ind.,  1897,  $1.25;  Powell, 
Geology  of  the  Uintah  Mountains,  Department  of  the  Interior,  Washington, 
1876  (out  of  print)  ;  Gilbert,  Geology  of  the  Henry  Mountains,  Depart- 
ment of  the  Interior,  Washington,  1877  (out  of  print). 

The  following  are  leading  magazines  of  geography,  at  least  one  of 
which  it  is  desirable  to  have  in  the  school :  Journal  of  Geography,  Chi- 
cago, 111.,  $1.50 ;  National  Geographic  Magazine,  Washington,  D.C.,  $2.50 ; 
Bulletin  of  the  American  Geographical  Society,  New  York,  $4.00  ;  Geographi- 
cal Journal,  London,  $6.00;  Scottish  Geographical  Magazine,  Edinburgh, 
$5.00. 

The  United  States  Geological  Survey  publishes  Bulletins,  Annual 
Reports,  Professional  Papers,  Monographs,  Folios,  and  Irrigation  Papers, 
many  of  which  contain  valuable  physiographic  material,  possibly  relating 
to  your  own  region. 


448 


INDEX. 


Absolute  humidity,  244. 

Absorption,  235. 

Abyssal  life,  197. 

Abyssinia,  peninsula  of,  25. 

Adirondacks,  107,  127,  301,  302. 

Adobe,  373. 

Africa,  24. 

Agassiz,  Lake,  78. 

Age  of  earth,  45. 

Ages,  geological,  415. 

Aggrading,  53. 

Agriculture,  Central  Plains,  311 ;  devel- 
opment of,  370;  New  England,  299; 
New  York,  302;  Piedmont  Belt,  307; 
western  United  States,  315. 

Air,  13, 18,  19,  229-250 ;  effect  of  gravity 
on,  231;  importance  of,  14;  impor- 
tance of,  to  animals,  353;  importance 
of,  to  plants,  336;  influence  of,  in 
weathering,  40;  in  ocean  water,  180; 
pressure  of,  255;  warming  of,  238. 

Air  pressure,  measurement  of,  421. 

Alabama  River,  329. 

Alaska,  glaciers  of,  139. 

Alaska,  peninsula  of,  23,  207,  222. 

Albany,  303. 

Aldrich  deep,  175. 

Aleutian  Islands,  volcanoes  of,  124. 

Alkali  flats,  87,  169,  324. 

Alleghany  plateau,  308,  310,  327. 

Allegheny,  309. 

Allegheny  River,  effect  of  ice  sheet  on, 
155,  156. 

Alluvial  fan,  66,  97,  321. 

Alpine  flora,  344. 

Alps,  94,  101,  102,  107,  108,  388 ;  glaciers 
of,  137,  141 ;  settlement  of,  105. 

Altitude,  effect  of,  on  temperature,  240; 
influence  of,  on  climate,  276. 

Amazon,  plains  of,  77. 


American  ice  sheet,  146. 

American  race,  382,  383. 

Amjihibia,  home  of,  359. 

Andes,  20,  24,  99,  107. 

Andesite,  412. 

Anemometer,  422. 

Aneroid  barometer,  422. 

Animals,  aid  of,  in  spread  of  plants,  345, 
346 ;  aid  of,  in  weathering,  41 ;  barri- 
ers to  spread  of,  361 ;  dependence  of, 
on  plants,  353 ;  distribution  of,  353- 
366;  domestic,  365,371;  fresh  water, 
358 ;  homes  of,  359 ;  in  Arctic,  354 ;  in 
Australia,  362;  influence  in  plant 
variation,  347 ;  influence  of  man  on, 
364;  influence  of  surroundings  on, 
353;  in  South  America,  363;  in  tem- 
perate zone,  356;  in  tropical  zone, 
357 ;  mode  of  life  of,  354 ;  of  desert, 
357 ;  on  islands,  361 ;  spread  of,  360 ; 
zones  of,  364. 

Annual  plants,  341. 

Antarctic  ice  sheet,  145. 

Antarctic  Ocean,  26. 

Anthracite  coal,  109,  413. 

Anticline,  37. 

Anticyclones,  263,  291,  292;  influence 
of,  on  weather,  265 ;  succession  of, 
263  ;  winds  of,  289. 

Antitrades,  260. 

Appalachian  belt,  308. 

x^ppalachian  Mountains,  23,  94,  99,  100, 
101,  102,  107. 

Appalachian  plateau,  84,  327. 

Arabia,  peninsula  of,  25. 

Aral  Sea,  162. 

Arctic  animals,  color  of,  355. 

Arctic  climates,  293,  294. 

Arctic  fauna,  354. 

Arctic  flora,  340. 

Arctic,  man  in,  384. 


443 


444 


NEW  PHYSICAL   GEOGRAPHY, 


Arctic  Ocean,  27. 
Argentina,  plains  of,  77. 
Argon,  229. 

Arid  lands,  western  United  States,  287. 
Arid  plains,  west,  326. 
Arid  plateaus,  inhabitants  of,  85. 
Arkansas  River,  325,  326. 
Arroyo,  87. 
Artesian  wells,  73. 
Ash,  volcanic,  122,  412. 
Asia,  25. 

Asia  Minor,  peninsula  of,  207. 
Asteroids,  4. 
Atlanta,  -308. 
Atlantic  Ocean,  27. 
Atmosphere,  13,  229-250. 
Atolls,  219,  222. 
Attraction  of  gravitation,  8. 
Augite,  407. 
Augusta,  75. 
Auk,  S&i. 

Aurora  australis,  419 
Aurora  borealis,  419. 
Australia,  25. 
Australia,  fauna  of,  362. 
Autumnal  equinox,  400. 
Avalanches,  44,  97. 
Avernus,  Lake,  117. 
Axis  of  earth,  inclination  of,  8. 
Azores  Islands,   124,  175,  222;  animals 
in,  362. 

B. 

Bad  Lands,  51. 

Bahama  Islands,  219,  222. 

Baikal,  Lake,  162. 

Balearic  Isles,  207. 

Balkash,  Lake,  162. 

Baltic  Sea,  26. 

Baltimore,  75,  102,  224,  307,  376. 

Banks,  fishing,  197  ;  in  sea,  208. 

Barograph,  422. 

Barometer,  421,  422. 

Barometric  gradient,  255. 

Barrier  beaches,  214,  222. 

Barrier  reefs,  218. 

Barriers,  to  spread  of  animals,  361 ;  to 

spread  of  plants,  345. 
Bars,  across  bays,  213 ;  offshore,  214. 
Basalt,  412. 
Baae  level,  55. 


Basin  Ranges,  93,  100,  324. 

Basins,  ocean,  175. 

Basques,  388. 

Bay  of  Fundy,  24 ;  tides  of,  187. 

Bay  of  St.  Lawrence,  24. 

Bayous,  328. 

Bays,  cause  of,  207-210,  223. 

Beaches,  210,  212,  213 ;  barrier,  214,  222; 

of  glacial  lakes,  150,  151. 
Beaver,  357 ;  effect  of,  in  forming  lakes, 

161. 
Belted  plain,  80. 
Belt  of  calms,  259,  279. 
Berlin,  376. 
Bermuda  Islands,  124,  175,  218,  222;  llf^ 

on,  361. 
Big  trees,  341. 
Bingharaton,  302. 
Biotite,  407. 
Birds,  home  of,  359. 
Birmingham,  310. 
Bison,  364,  366. 
Bituminous  coal,  410. 
Black  Hills,  310. 
Black  race,  382,  383. 
Blake  deep,  175. 
Blizzards,  289. 
Bluffs,  river,  61,  327. 
Bogs,  168. 
Bog  iron  ore,  410. 
Bombs,  volcanic,  122. 
Bonneville,  Lake,  164 ;  shore  lines  of,  220. 
Bore,  188. 
Bosses,  34,  127. 

Boston,  217,  224,  300;  drumlins  of,  153. 
Boston  Harbor,  208. 
Bowlder  beaches,  212. 
Bowlder  clay,  142,  152. 
Bowlders,  erratic,  142. 
Bowlder  trains,  152. 
Brazos  River,  329. 
Breakers,  185. 
Bridgeport,  300. 
British  Isles,  25,  208,  210;  reasons  foi 

importance  of,  389. 
Brooklyn,  305. 
Brown  race,  382,  383. 
Brussels,  376. 
Buffalo,  156,  166,  302,  303,  304,  313,  331. 

376. 


INDEX. 


445 


Building  materials,  373.  i 

Buttes,  83. 

C. 

Cactus,  343. 

Cairo,  327. 

Calabria,  earthquakes  in,  131. 

Calcareous  tufa,  409,  410. 

Calcite,  34,  407. 

Calderas,  120,  121,  123. 

California,  filling  of  valley  of,  67,  68. 

California,  Gulf  of,  207. 

Callao,  224. 

Calms,  belt  of,  259,  279. 

Camel,  89,  358. 

Campos,  283. 

Canary  Islands,  124,  175,  222. 

Canyons,  81,  320,  321  ;  Colorado,  322,  323. 

Cape  Canaveral,  213. 

Cape  Cod,  213,  215. 

Cape  Fear,  213. 

Cape  Hatteras,  213,  215. 

Cape  Lookout,  213. 

Cape  Verde  Islands,  124,  175. 

Capes,  cause  of,  207-210,  222,  223. 

Carbonate  of  lime  in  ocean,  180. 

Carbon  dioxide,  229;  importance  of,  to 

plants,  336. 
Caribbean  Sea,  23,  207. 
Cascade  Ranges,  126. 
Caspian  Sea,  162,  163. 
Castine,  224. 

Catskill  Mountains,  98,  107,  301,  302. 
Caucasian  race,  382,  383. 
Cave  dwellers,  85. 
Caverns,  59. 
Cayuga  Lake,  153,  303. 
Centigrade  scale,  420. 
Central  Plains,  76,  310. 
Chad  Lake,  162. 
Challenger  deep,  175. 
Champlain,  Lake,  162,  165. 
Change  of  level  of  land,  24,  35,  204. 
Charleston,  306;  earthquake,  1.31. 
Chasms,  211. 

Chemically  formed  rocks,  409,  410. 
Chesapeake  Bay,  24,  74,  209,  306,  329. 
Chicago,  31,  150,  151,  166,  220,  313,  376. 
China  Sea,  207. 
Chinook,  290. 
Cincinnati,  156,  312,  376. 


Circurapolar  whirl,  260. 

Cirques,  142. 

Cirrus  clouds,  248. 

Cities,  location  of,  375. 

Civilization,  ancient,  387;  influence  of 
commerce  on,  378. 

Clastic  rocks,  409,  410. 

Clay  beds,  409,  410. 

Cleveland,  166,  220,  313. 

Cliff  dwellers,  85. 

Cliffs,  sea,  211. 

Climate,  275-295;  Arctic,  293,  294;  belt 
of  calms,  279;  continental,  288;  east 
coasts,  288;  equable,  238;  Indian,  284; 
influence  of  altitude  on,  276;  influ- 
ence of  lakes  on,  165,  166;  influence 
of  ocean  currents  on,  278;  influence 
of,  on  plants,  339;  influence  of  topog- 
raphy on,  279;  influence  •  of  water 
on,  277;  influence  of  winds  on,  278; 
mountain,  95;  plateau,  83;  south 
temperate  zone,  293;  southwestern 
United  States,  316 ;  temperate  zones, 
285-293;  west  coasts,  286. 

Climbing  bogs,  168. 

Clothing,  371. 

Cloudbursts,  86,  268. 

Clouds,  247. 

Coal,  108,  170,  410,  411 ;  Appalachians, 
309;  Central  Plains,  312,  313. 

Coastal  plains,  72,  305;  swamps  on,  169. 

Coast  lines,  203-225;  changes  in,  204; 
of  drowned  lands,  208;  elevated  sea 
bottom,  205;  influence  on  man,  389; 
irregularities  of,  23-26;  irregular 
mountainous,  207 ;  life  history  of,  221 ; 
New  England,  299;  sinking  of,  74; 
straight  mountainous,  206. 

Coast  Ranges,  99. 

Cold-blooded  animals,  353. 

Cold  pole,  288. 

Cold  waves,  29G. 

Color,  232,  233;  of  Arctic  animals,  355; 
of  ocean  water,  181. 

Colorado  Canyon,  56,  82,  316,  322-323. 

Colorado  plateau,  322,  324. 

Colorado  River,  87,  322;  of  Texas,  329. 

Columbia  lava  plateau,  125,  320. 

Columbia  River,  320. 

Columbia,  S.C.,  75. 


446 


NEW  PHYSICAL   GEOGRAPHY. 


Combustion,  229. 

Commerce,  development  of,  377. 

Compass,  418. 

Conduction,  236. 

Cone  deltas,  66. 

Cones,  forms  of  volcanic,  123. 

Conglomerates,  409,  410. 

Connecticut  River,  329. 

Connecticut  valley,  298. 

Consequent  course,  55. 

Consequent  mountain  drainage,  103. 

Constantinople,  376. 

Continental  climate,  288. 

Continental  glaciers,  146. 

Continental  shelf,  72. 

Continental  slope,  22. 

Continents,  22-26;    climate  of  interior 

of,  288;  elevation  of,  22;  influence  of 

form  on  man,  2(5. 
Contour  interval,  429. 
Contour  maps,  428. 
Contraction,  99. 
Convection,  236. 
Coral  reefs,  217,  222. 
Cordillera,  95. 
Cordilleras,  western,  23. 
Corrosive  work,  52. 
Corsica,  25,  207. 
Crater  Lake,  121,  123. 
Crest  of  waves,  185. 
Crete,  207. 

Crevasses,  138;  in  levees,  62,  328. 
Crinoids,  198. 
Crumpling  of  strata,  37. 
Crust,  movement  of,  35. 
Cultivated  plants,  348. 
Cumulus  clouds,  248,  268. 
Cusps,  213. 
Cyclonic  storms,  262,  291,  292;  cause  of, 

264;    influence   of,  on  weather,  265; 

paths  followed  by,  264;  succession  of, 

263;  winds  of,  289. 
Cypress,  .344. 
Cyprus,  207. 

D. 

Daily  range,  241. 

Dead  Sea,  22, 161, 163 ;  lack  of  life  in,  359. 

Death  Valley,  324. 

Debris  cones,  97. 


Deccan,  lava  plateau  of,  126. 

Deciduous  trees,  340. 

Declination,  418,  419. 

Deep-sea  exploring,  173, 174 ;  life  in,  197. 

Deeps,  ocean,  175. 

Degrading,  53. 

Degrees,  402. 

Delaware  Bay,  24,  209,  306,  329. 

Delaware  River,  329. 

Delta,  Mississippi,  328. 

Deltas,  64,  222 ;  lake,  162,  164. 

Denmark,  peninsula  of,  208. 

Density  of  sea  water,  181. 

Denudation,  45;  of  mountains,  96. 

Denver,  315,  376. 

Desert  fauna,  357. 

Desert  flora,  342. 

Deserts,  86-89;  as  barriers  to  spread  of 
animals,  361 ;  as  barriers  to  spread  of 
plants,  346;  drainage  of,  86;  life  on, 
88;  man  in,  386;  nature  of,  86;  rain- 
fall of,  86;  trade  wind,  281;  wind 
work  in,  87. 

Detroit,  166,  313. 

Dew,  246. 

Dew  point,  245. 

Diabase,  411,  412. 

Diathermanous,  234. 

Diatom  ooze,  177. 

Diffraction,  233. 

Dike,  34,  126. 

Diorite,  411,  412. 

Dip,  37  ;  compass,  418. 

Dismal  swamp,  74,  169. 

Distributaries,  64,  65,  328. 

Distribution,  of  animals,  353-366;  of 
mankind,  381,  383. 

Dodo,  364. 

Doldrums,  259. 

Dolomite,  407,  411. 

Dome-shaped  mountains,  100. 

Domestic  animals,  365,  371. 

Dormant  volcanoes,  115. 

Downes,  283. 

Drainage,  of  deserts,  86;  of  mountains, 
103. 

Dredging,  174. 

Drift,  glacial,  147, 154 ;  ocean,  191 ;  strati- 
fied, 149. 

Droughts,  286,  291. 


tni)E^. 


447 


Drowned  coasts,  208. 
Drowned  river,  330. 
Drumlins,  152. 
Duluth,  166,220,311,313. 
Dust  particles,  230  ;  efifect  of,  on  fog, 
247. 

E. 

Early  man,  369. 

Earth,  age  of,  45;  as  a  planet,  1-10; 
contraction  of,  18,  35,  99 ;  differences 
in  temperature  on,  239;  general  fea- 
tures of,  13-28 ;  interior  of,  17 ;  proof 
of  roundness,  2;  radiation  from,  235; 
rotation  of,  6 ;  shape  of,  1 ;  size  of,  3 ; 
solid,  16;  wind  systems  of,  258. 

Earth's  axis,  inclination  of,  8. 

Earth's  crust,  18;  changes  in,  20,  21,  31- 
46;  irregularities  of,  19. 

Earthquake  waves,  186. 

Earthquakes,  101 ,  130-132 ;  cause  of,  130 ; 
characteristics  of,  131 ;  effects  of,  131 ; 
occurrence  of,  130. 

East  coasts,  climate  of,  288. 

East  Indies,  25,  98,  207,  222. 

Ebb  of  tide,  187. 

Eclipse,  2. 

Eifel  district,  volcanoes  of,  123. 

Elevated  beaches,  220. 

Elevated  sea-bottom  coasts,  205. 

Elevation,  forces  of,  21. 

Ellipse,  5. 

Elmira,  302. 

Energy,  radiant,  234. 

Epicentrum,  131. 

Epiphytes,  338,  342. 

Equable  climate,  238,  277. 

Equator,  402. 

Equatorial  drift,  191. 

Equinoxes,  400. 

Erie  Canal,  303. 

Erie,  Lake,  161,  162. 

Erosion,  agencies  of,  21,  44;  glacial,  138, 
153. 

Erratics,  141,  153. 

Eskimo,  294,  371,  372,  373,  384. 

Ethiopian  race,  382,  383. 

Etna, 118,  130. 

Euphrates,  early  civilization  in,  387. 

Eurasia,  25. 

Europe,  25. 


Evaporating  pan,  424. 

Evaporation,    230;     measurement    of, 

424. 
Everglades,  169. 
Evergreen  trees,  340. 
Evolution,  347,  360. 
Exchange,  primitive,  377. 
Excursions,  field,  439. 

P. 

Fahrenheit  scale,  420. 

Fall  Line,  75,  306,  307. 

Fall  River,  300. 

Far  West,  314. 

Fault,  37. 

Fault-block  mountains,  93,  100. 

Fauna,  354:  Australian,  362;  of  Arctic, 
354 :  of  desert,  357 ;  fresh-water,  358 ; 
island,  361;  of  northern  continents, 
363;  South  American,  363;  temper- 
ate, 356;  tropical,  357. 

Feldspar,  34,  406. 

Field  work,  439. 

Fingal's  Cave,  127. 

Finger  Lakes,  153. 

Fiords,  26,  153,  209. 

Fishing  banks,  197. 

Floodplains,  58,  61,  327,  328. 

Floods,  Mississippi,  328. 

Flora,  339:  Alpine,  344;  Arctic,  340;  of 
deserts,  342;  of  mountains,  343;  of 
savannas,  342;  of  steppes,  342;  sub- 
tropical, 342;   temperate,  340;   tropi- 

Florida,  frosts  in,  286;  plain,  74;  plain, 

drainage  of,  55. 
Flow  of  tide,  187. 
Focus  of  earthquake,  131. 
Foehn,  290. 
Fog,  247. 

Food  of  man,  370. 
Forest,  care  of,  349, 
Forestry,  350. 
Fracture,  zone  of,  18. 
Fragmental  rocks,  409,  410. 
Fresh-water  fauna,  358. 
Fringing  reefs,  218. 
Frost,  235,  246;  aid  of,  in  weathering, 

40. 
Fur-bearing  animals,  353,  355,  356,  357. 


448 


NEW  PHYSICAL    GEOGRAPHY, 


G. 

Galapagos  Islands,  animals  in,  362. 

Galveston,  73,  214,  215,  224,  30(i;  effect 
of  hurricane  on,  271. 

Gas,  19. 

Geneva  Lake,  103. 

Genoa,  37(5. 

Geological  Ages,  415. 

George,  Lake,  1G5. 

Geiirges  Banks,  197. 

Geysers,  132,  133. 

Giant's  Causeway,  127. 

Gibraltar,  223. 

Glacial  drift,  147. 

Glacial  erosion,  138,  153. 

Glacial  lakes,  shore  lines  of,  220. 

Glacial  period,  147;  cause  of,  147. 

Glaciers,  137-150;  Alaskan,  139;  distri- 
bution of  valley,  141 ;  effects  of  con- 
tinental on  Mississippi  system,  327; 
effect  of  continental  in  New  England, 
299;  effect  of  continental  in  Central 
Plains,  310;  former  extension  of  val- 
ley, 141 ;  Greenland,  143  ;  intiuence  of 
continental  on  New  York,  301;  val- 
ley, 137-142. 
.Glasgow,  224. 

Globigerina  ooze,  177. 

Gneiss,  34,35,413. 

Government,  origin  of,  375. 

Grade,  56. 

Graham  Island,  112. 

Grand  Banks,  197. 

Grand  Canyon  of  Colorado,  81,  322. 

Grand  River,  322. 

Granite,  34,  35,  411,  412. 

Graphite,  413. 

Gravel  beds,  409,  410. 

Gravitation,  attraction  of,  8. 

Gravity,  8;  effect  of,  on  air,  2.31;  effect 
of,  on  plants,  338;  influence  of,  on 
animals,  354. 

Grazing,  western  United  States,  314. 

Great  Barrier  Reef,  218. 

Great  Basin,  324. 

Great  Bear  Lake,  162. 

Great  Falls,  326. 

Great  Lakes.  161,  162,  165,  166,  329,  .330; 
origin  of,  156;  post-glacial  history  of, 
160,  151 ;  water  route,  311. 


Great  Plains',  77,  326;  ranching,  311. 

Great  Salt  Lake,  78,  163,  164,  324. 

Greece,  peninsula  of,  25,  98,  207. 

Greeks,  ancient,  377. 

Green  River,  322. 

Greenland,  absence  of  plants  in,  336; 

ice  desert,  86;  ice  sheet,  143;  interior 

of,  144. 
Greenwich  Observatory,  404. 
Ground  moraine,  138. 
Ground  swell,  185. 
Guam,  175. 

Gulf  of  California,  23. 
Gulf  of  Mexico,  23. 
Gulf  Stream,  192,  289. 
Gulfs,  cause  of,  207-210,  223. 
Gypsum,  167,  408,  410. 


Hachure  maps,  428. 

Hail,  250. 

Hair  hygrometer,  423. 

Halos,  233. 

Hanging  valleys,  142,  153. 

Harbors,  223-225;  cause  of,  207-210. 

Hardheads,  152. 

Hartford,  300. 

Hawaiian  Islands,  20,  98,  175,  222 ;  ani- 
nials  in,  362;  volcanoes  of,  119-121, 
123. 

Haze,  230. 

Headland  cliffs,  212. 

Headwater  erosion,  104. 

Heat,  234-237;  in  earth's  interior,  17; 
from  sun,  10;  latent,  238;  of  vapori- 
zation, 238;  zones  of,  275. 

Hell  Gate,  tides  of,  188. 

Hematite,  408. 

Henry  Mountains,  100. 

Herculaneum,  destruction  of,  115-117. 

High  barometer,  421. 

High  pressure,  255. 

High-pressure  areas,  263. 

Himalayas,  102,  106,  388;  rainfall  at 
base  of,  284. 

Hoangho  River,  67. 

Hoboken,  305. 

Homes,  selection  of,  374. 

Homes  of  animals,  359. 

Hooks,  213. 


II^DEX. 


449 


Hornblende,  407. 

Horse  latitudes,  261 ;  rainfall  of,  285. 

Hot  springs,  132. 

Houses,  372,  373,  374. 

Hudson  Bay,  24. 

Hudson  River,  329:  drowning  of,  304. 

Humboldt  glacier,  144. 

Humidity,  244. 

Huron,  Lake,  161,  162. 

Hurricanes,  269;  effects  of,  271. 

Hygrometer,  423. 

I. 

Ice,  aid  in  river  erosion,  53. 

Icebergs,  194,  195  ;  formation  of,  145. 

Iceberg  waves,  186. 

Ice  cave,  139. 

Ice-dammed  lakes,  149. 

Ice  fall,  138. 

Ice  floes,  194. 

Ice  in  ocean,  194. 

Ice  packs,  194. 

Iceland,  lava  plateau  of,  126;  volcanoes 

of,  124. 
Ice  sheet,  143;  Antarctic,  145;    Arctic, 

145;    eifects    of,    154;    former,    146; 

Greenland,  143. 
Igneous  rocks,  33,  408,  411,  412. 
India,  climate  of,  284 ;  peninsula  of,  25. 
Indian  Ocean,  27. 
Indian  race,  382,  383. 
Indians,  385,  387. 
Indo-China,  peninsula  of,  25. 
Inhabitants  of  plateaus,  84,  85. 
Insects,  home  of,  359. 
Instrument  shelter,  424,  425. 
Instruments,  meteorological,  420-425. 
Interior  basins,  22,  95. 
Interior  of  earth,  17. 
Intermittent  desert  streams,  87. 
Intruded  igneous  rocks,  34,  126,  411. 
Invertebrates,  home  of,  359. 
Irish  Sea,  26. 
Iron,  Appalachians,  309;  Central  Plains, 

312,  313 ;  deposits  of,  410 ;  ores  of,  408. 
Iron  pyrite,  408. 
Irrigation,  315. 
Ischia,  island  of,  117. 
Islands,    cause   of,    207-210,    222,  223; 

faunas  of,  361. 
2g 


Isobars,  262. 
Isogenic  map,  419. 
Isothermal  chart,  276. 
Isotherms,  276. 
Isthmus  of  Panama,  24. 
Italy,  peninsula  of,  25,  98,  207. 


James  River,  329. 

Japan,  earthquakes  in,  130. 

Japanese  Islands,  20,  25,  98,  207,  222. 

Japan  Sea,  207. 

Jersey  City,  305. 

Jetties,  328. 

Joint  planes,  38 ;  influence  on  rivers,  63. 

Jura,  94,  100. 

K. 

Kamchatka,  peninsula  of,  25,  98. 

Kames,  149. 

Kangaroo,  362. 

Kaolin,  407. 

Kettles,  moraine,  148. 

Key  West,  222. 

Kilauea,  119,  120. 

Korea,  peninsula  of,  25,  222. 

Krakatoa,  119,  123. 

Kurile  Islands,  22,  98. 

L. 

Laboratory  equipment,  431-438. 

Labrador  Current,  193,  279,  289. 

Labrador  peninsula,  23. 

Laccolith,  127. 

Lachine  rapids,  330. 

Ladrone  Islands,  175. 

Lake  basins,  origin  of,  160. 

Lake  plains,  78. 

Lakes,  160-167 ;  as  resorts,  165;  freezing 
of,  165, 166;  glacial,  156;  ice-dammed, 
149 ;  importance  of,  165 ;  influence  on 
climate,  165,  166;  influence  on  navi- 
gation, 166;  life  history  of,  164;  ox- 
bow, 63,  328;  salt,  163;  shores  of, 
220 ;  size  and  form  of,  161 ;  storage  of 
water  in,  167. 

Lake  Superior  highlands,  310. 

Land  breezes,  256. 

Land,  changes  in  level  of,  35,  204;  sink- 
ing of,  24 ;  warming  of,  237. 

Land  hemisphere.  27. 


450 


^E^\'  i'H^iiiiJAL  geography. 


Landslides.  44,  97. 

I^a  Soufriere,  eruption  of,  113-115. 

Lassen  Peak,  121. 

Latent  heat,  238;  liberation  of,  266. 

Lateral  moraine,  138. 

Latitude,  402. 

Lava,  33;  Hawaiian  volcanoes,  120, 121. 

Lava  floods,  125. 

Lava  flows,  122. 

Lava  intrusions,  126. 

Lava  plateau,  81;  Columbia,  320. 

Lava  soils,  130, 

Lawrence,  155,  300,  371. 

Leads  in  ocean  ice,  194. 

Left-hand  deflection,  258. 

Levees,  62,  328. 

Life,  on  deserts,  88;  in  ocean,  195-198; 
on  ocean  bottom,  197. 

Life  history,  of  coast  line,  221 ;  of  lakes, 
164;  of  mountains,  101;  of  river  val- 
leys, 54 ;  of  volcanoes,  128. 

Light,  232;  relation  of  plants  to,  337. 

Lightnmg,  268. 

Lignite,  410,  411. 

Limestone,  33,  35,  410. 

Limonite,  408. 

Lipari  Islands,  113, 

Liquid,  19. 

Littoral  life,  196. 

Liverpool,  376. 

Llanos,  283. 

Lobate  moraines,  148. 

Loess,  151. 

London,  210,  376;  fog  of,  247. 

Long  Island,  24. 

Long  Island  Sound,  24. 

Longitude,  403. 

Los  Angeles,  316. 

Louisville,  312. 

Low  barometer,  421. 

Lower  California,  23,222;  peninsula  of, 
98. 

Low  pressure,  255 ;  areas,  262. 

Luray  Cave,  60. 


M. 


Madagascar,  25,  222. 
Madeira  Islands,  222. 
Madrid,  376. 
Magnetic  north,  418. 


Magnetic  poles,  418. 

Magnetism,  418. 

Magnetite,  408. 

Malaria,  170. 

Malaspina  glacier,  140. 

Malay  Peninsula,  98,  207,  222. 

Malay  race,  382,  383. 

Mammals,  home  of,  359. 

Mammoth,  360,  363,  364. 

Mammoth  Cave,  59. 

Man,  aid  of,  in  spreading  plants,  345; 
in  Arctic,  384 ;  barriers  overcome  by, 
381 ;  dependence  of,  on  nature,  369 ;  in 
desert,  386;  domestication  of  animals 
by,  365 ;  early,  369 ;  effect  in  forming 
lakes,  161 ;  effect  of  ice  sheet  on,  154- 
156;  effects  of  ocean  currents  on,  193, 
194  ;  effects  of  tides  on,  189;  eft'ect  of 
valley  form  on,  58;  food  of,  370  ;  im- 
portance of  shore  lines  to,  203;  influ- 
ence of  coast  line  on,  389;  influence  of 
continent  form  on,  26;  influence  of 
deltas  on,  65;  influence  of  deserts  on, 
88;  influence  of  lakes  on,  165,  167 ;  in- 
fluence of  mountains  on,  105-109,  388; 
influence  of  ocean  on,  15,  28;  influ- 
ence of  swamps  on,  170;  influence  on 
animals,  364 ;  influence  on  nature,  379 ; 
influence  on  plant  variation,  348;  in 
temperate  zone,  385;  in  tropical  zone, 
385 ;  plants  of  value  to,  348 ;  relation 
of  plateaus  to,  84,  85 ;  relation  of,  to 
land,  31 ;  relation  of  volcanoes  to,  129 ; 
spread  of,  381. 

Man  and  nature,  369-392. 

Manchester,  155. 

Mangrove,  344;  swamps,  217. 

Mankind,  development  of,  369-380;  dis. 
tribution  of,  381-383 ;  races  of,  382,  38c. 

Manufacturing,  Appalachians,  309 ;  Nev 
England,  299. 

Maps,  428 ;  for  laboratory  use,  431-4ov.  - 
mounting  of,  437  ;  use  of,  432. 

Marble,  34,  35,  413. 

Marshes,  salt,  216. 

Marsupials,  362. 

Massachusetts  Bay,  208. 

Mastodon,  360,  363,  364. 

Mature  coast  line,  221. 

Mature  mountains,  10^. 


INDEX. 


451 


Mature  plains,  79. 

Mature  valleys,  57. 

Mauna  Kea,  119,  120. 

Mauna  Loa,  119,  120.  v 

Meanders,  62,  328. 

Medial  moraine,  138. 

Mediterranean,  207, 208 ;  climate  of,  279 ; 
early  commerce  in,  377 ;  tides?  of,  187. 

Memphis,  327.  | 

Meridian,  403. 

Mesas,  82,  83.  . 

Mesquite,  343. 

Metamorphic  rocks,  34,  408,  413. 

Meteorological  instruments,  420-425. 

Mexico,  Gulf  of,  207. 

Mica,  407. 

Michigan,  Lake,  161,  162. 

Mid- Atlantic  Ridge,  175. 

Milan,  376. 

Milwaukee,  166,  313. 

Minerals,  406-408. 

Mineral  wealth,  Central  Plains,  312 ;  of 
mountains,  108. 

Mining,  Appalachians,  309;  western 
United  States,  315. 

Minneapolis,  155,  .311,  312. 

Mirage,  232. 

Mississippi,  delta  of,  65,  328;  drainage 
area  of,  320 ;  river,  310,  312 ;  rock  load 
of,  52 ;  system,  325-328 ;  valley  of,  76, 
77,  310,  325,  328. 

Missouri  river,  325,  326,  327. 

Mobile,  306;  bay  of,  209. 

Models,  428. 

Mohave  desert,  282. 

Moist  plateaus,  inhabitants  of,  84. 

Monadnock,  298. 

Money,  origin  of,  378. 

Mongolian  race,  382,  383. 

Monoclinal  shifting,  law  of,  104. 

Monocline,  37. 

Monotreraes,  362. 

Monsoon  winds,  256,  259^  284. 

Monte  Somma,  115. 

Mont  Pele,  eruption  of,  113-115. 

Montreal.  313,  330. 

Moon,  3,  6,  18. 

Moraines,  138;  terminal,  148;  of  reces- 
sion, 148. 

Mountain  flora  343. 


Mountainous  coasts,  206-208. 

Mountains,  93-109;  Appalachians,  .308; 
as  barriers,  106,  308;  as  barriers  to 
spread  of  animals,  ;^1 ;  as  barriers  to 
spread  of  plants,  346;  cause  of,  99; 
climate  of,  95;  crossing  of,  106;  de- 
nudation of,  96;  distribution  of,  98; 
drainage  of,  103;  effect  of,  on  climate, 
286,  287;  height  of,  20;  influence  on 
man,  388 ;  life  history  of,  101 ;  mineral 
wealth  of,  108 ;  names  applied  to  parts 
of,  94;  relation  of  continents  to,  22; 
resemblance  to  plateaus,  98  ;  rocks 
of,  93;  settlement  of,  105;  as  summer 
resorts,  107 ;  as  timber  reserves,  107  ; 
types  of,  100. 

Mountain  valley  breezes,  256. 

Mount  Ararat,  124. 

Mount  Everest,  20. 

Mount  Holyoke,  127,  298. 

Mount  Hood,  124,  1.30. 

Mount  Mazama,  122. 

Mount  Rainier,  124,  130. 

Mount  St.  Elias,  140. 

Mount  St.  Helens,  124. 

Mount  Shasta,  121,  124,  130. 

Mount  Tom,  127,  298. 

Mount  Washington,  34. 

Mounting  of  maps,  4.37. 

Mud  flows,  115,  122. 

Muir  glacier,  139. 

Muscovite,  407. 

N. 

Natural  bridge,  60. 
Natural  levee,  62. 

Navigation,  development  of,  377,  378. 
Neap  tides,  189,  417. 
Nebula,  18. 
Neck,  volcanic,  126. 
Negro  race,  382,  383. 
Netherlands,  170. 
Neve',  137. 
New  Bedford,  300. 
New  England,  298. 
Newfoundland,  24,  208,  210,  247. 
New  Haven,  300. 

New  Orleans,  224,  286,  306,  312,  376. 
New  York  City,  102,  210,  224,  304-305, 
376. 


452 


NEW  PHYSICAL   GEOGRAPHY. 


New  York  Harbor,  224. 
Xe^v  York  State,  301-305. 
New  Zealand,  98,  222. 
Niagara  Falls,  54,  155,  329,  331-334;  re- 
cession of,  332,  333. 
Niagara  River,  5(5,  164,  167,  330,  333. 
Nicaragua  Lake,  130.  i 

Nile  delta,  64. 
Nile  River,  87. 

Nile  valley,  early  civilizationau,  387. 
Nimbus  clouds,  248. 
Nitrogen,  229. 
Nomads,  89,  386,  387. 
Norfolk,  306. 
North  America,  23. 
North  Atlantic  eddy,  192. 
Northeast  storms,  266. 
Northeast  trades,  259. 
Northers,  289. 
North  magnetic  pole,  418. 
North  pole,  climate  near,  294. 
North  Sea,  26. 
Norway,  fiords  of,  209. 
Xova  Scotia,  peninsula  of,  208. 
Nuuatak,  144. 
Nyassa,  Lake,  162. 


')ases,  89,  387. 

)bsidian,  412. 

Dcean  basins,  175. 

Ocean  bottom,  173-179;  deposits  on, 
176;  life  on,  197;  light  on,  182;  tem- 
perature of,  183,  184;  topography  of, 
178. 

•Jcean  currents,  190-194;  aid  of,  in 
spreading  plants,  345;  effects  of,  193; 
influence  of,  on  climate,  278. 

"Oceanography,  173. 

)ceans,  14, 173-198;  as  barriers  to  spread 
of  animals,  361 ;  as  barriers  to  spread 
of  plants,  346;  depth  of,  14,  20,  174, 
175,  176;  ice  in,  194;  importance  of, 
15;  life  in,  195-198;  temperature  of, 
182-184 ;  form  of,  26. 

*cean  water,  color  of,  181 ;  composition 
of,  179;  density  of,  181;  movements 
of,  184-195;  pressure  of,  181. 

Off s'aore  bars,  214,  222. 
C'.f'.hore  platforms,  212. 


Ohio  River,  325,  327 ;  effect  of  ice  sheet 

on,  155,  156. 
Old  mountains,  102. 
Old  plain,  79. 
Old  valleys,  58. 
Ontario,  Lake,  154,  161,  162. 
Oolite,  409,  410. 
Oozes,  ocean  bottom,  176. 
Orbit,  earth's,  397. 
Organic  rocks,  410. 
Orinoco  delta,  65. 
Ottawa  River,  330. 
Overturned  folds,  37. 
Ox-bow  cut-off,  63,  328. 
Oxygen,  13,  229. 


Pacific  Ocean,  27. 

Pack  ice,  194. 

Palisades,  127,  411. 

Parallels  of  latitude,  402. 

Paris,  376. 

Park  lands,  283. 

Parks,  mountain,  95. 

Passes,  at  Mississippi  mouth,  328. 

Pass,  mountain,  95. 

Peaks,  mountain,  95. 

Peat  bogs,  168,  170,  410,  411. 

Pelagic  life,  195. 

Peneplain,  58,  102,  307. 

Peninsulas,  cause  of,  207-210,  222,  223. 

Perennial  plants,  341. 

Philadelphia,    31,    75,    102,    224,    307, 

376. 
Philippine  Islands,  20,  22,  25,  98,  207, 

222. 
Phosphate,  306. 
Phosphorescence,  182. 
Physiography,  32;    of    United    States. 

298-317. 
Picture  writing,  379. 
Piedmont  Belt,  102,  307,  308. 
Piedmont  glacier,  140. 
Pikes  Peak,  34. 

Pittsburg,  31,  156,  309,  312,  327,  376. 
Plains,  72-80 ;  central  United  States,  76- 

314;  classes  of,  79;   coastal,  72,  305- 

307;  continental  shelf,  72;  industries 

of,  77;  lake,  78;   life  history  of,  79; 

New   York,  303;    relation    to  moun' 


INDEX 


453 


tains,  22;  Russian,  75;  Siberian,  75; 
submarine,  175. 
Plane  of  ecliptic,  397. 
Planets,  3-6. 

Plant  food,  40. 

Plants,  aid  in  weathering,  40;  Arctic, 
340;  barriers  to  spread  of,  345;  con- 
ditions influencing,  336-339;  depen- 
dence on,  of  animals,  353;  of  des- 
erts, 342;  distribution  of,  336-350; 
effect  of  gravity  on,  338;  importance 
of  air  to,  336;  importance  of  soil  to, 
338 ;  importance  of  sunlight  to,  337  ; 
importance  of  "water  to,  337 ;  influ^ce 
of  climate  on,  339;  means  of  distri- 
bution of,  345;  of  mountains,  343; 
relation  of,  to  temperature,  336;  of 
savannas,  342;  of  steppes,  342;  tem- 
perate, 340;  tropical,  342;  of  value  to 
man,  348  ;  variation  in,  346 ;  water,  344. 

Plateaus,  80-85 ;  Alleghany,  308-310, 327 ; 
Appalachian,  308-310;  climate  of,  83; 
Colorado,  322,  324;  inhabitants  of,  84, 
85;  lava,  81;  nature  of,  80;  New 
York,  302;  relation  to  continents,  22; 
resemblance  to  mountains,  98;  sculp- 
turing of,  81. 

Platte  River,  325,  327. 

Platypus,  duck-billed,  362. 

Playas,  169,  324. 

Pock€t  beaches,  212. 

Po,  filling  of  valley  of,  68. 

Poles,  magnetic,  418. 

Pompeii,  destruction  of,  115-117. 

Porphyritic  crystals,  412. 

Portland,  Maine,  300;  Oregon,  210,  316, 
321. 

Pot  holes,  64 ;  glacial,  138. 

Potomac  River,  329. 

Prairies,  77. 

Precipitation,  245. 

Pressure,  air,  255;  of  sea  water,  181. 

Prevailing  westerlies,  260;  variable 
winds  of,  289. 

Prime  meridian,  404. 

Promontories,  cause  of,  207-210,  222. 

Providence.  300. 

Psychrometer,  423. 

Pteropod  ooze,  177- 

Pueblos,  85. 


Pumice,  34,  112,  122,  412. 
Pyrenees,  106,  388. 
Pyrites,  408. 

Q. 

Quaking  bogs,  168. 
Quartz,  34,  406. 
Quartzite,  34,  35,  513. 
Quicksands,  212. 

R. 

Races,  of  mankind,  382. 

Races,  tidal,  188. 

Radiant  energy,  234 ;  passage  of,  234. 

Radiation,  234;  from  earth,  235. 

Rain,  249;  cause  of,  in  cyclonic  storms, 
26{). 

Rainbows,  233. 

Raindrops,  249. 

Rainfall,  at  base  of  Himalayas,  284; 
belt  of  calms,  280;  influence  of  cy- 
clones and  anticyclones  on,  266; 
measurement  of,  424;  of  deserts,  86, 
282;  of  temperate  zones,  285;  of 
trade-wind  belts,  280,  281;  of  west 
coasts,  286;  on  mountains,  96. 

Rain  gauge,  424. 

Rain  sculpturing,  51. 

Raleigh,  75. 

Ranching,  Great  Plains,  311. 

Range,  mountain,  94. 

Rarefied  air,  231. 

Red  clay,  177. 

Red  Race,  382,  383. 

Red  River,  325,  327. 

Red  River  of  the  North,  valley  of,  78» 
150,  320. 

Red  Sea,  207. 

Reflection,  232,  235. 

Refraction,  ^32. 

Reindeer,  384. 

Rejuvenated  rivers,  83. 

Relative  humidity,  244. 

Relief  maps,  428. 

Reptiles,  home  of,  359. 

Residual  soil,  43. 

Revolution,  5,  397,  398;  effects  of,  7. 

Rhine  delta,  66,  170. 

Rhyolite,  411,  412. 

Richmond,  75. 


454 


NEW  PHYSICAL   GEOGRAPHY. 


Ridge  road,  150. 

Ridges,  mountain,  95. 

Righit-hand  deflection,  258. 

Rio  Grande,  324. 

Rio  Pecos,  325. 

River  capture,  104. 

River  pirate,  104. 

Rivers,  aid  of,  in  spreading  plants,  345 ; 
effect  of  ice  on,  53;  effect  of  glacial 
ice  on,  156 ;  erosive  work  of,  52 ; 
floodplains  of,  61;  grade  of,  56;  ma- 
ture valleys  of,  57;  mountain,  103; 
old  valleys  of,  58;  rejuvenated,  83; 
rock  load  of,  51 ;  superimposed,  83 ; 
supply  of  water,  50;  of  United  States, 
320-334 ;  variation  in  volume  of,  50. 

River  swamps,  169. 

River  terraces,  63. 

River  valleys,  50-68 ;  life  history  of,  54. 

Roches  moutonnees,  142,  153. 

Rochester,  155,  22),  303,  376. 

Rock,  19;  beneath  soil,  16. 

Rock  basins,  142. 

Rock  flour,  139. 

Rocks,  408-413 ;  chemically  formed,  409, 
410 ;  classification  of,  408 ;  clastic,  409, 
410;  fragmental,  40J),  410;  igneous, 
408,  411,  412;  metamorphic,  408,  413; 
Minerals  in,  408;  mountain,  93,  94; 
of  crust,  32;  organic,  410;  resistance 
of,  34;  sedimentary,  408-410;  sedi- 
mentary, consolidation  of,  33. 

Rocky  Mountains,  99,  101, 107. 

Rollers,  185. 

Rome,  376. 

Rome,  N.Y.,  303. 

Rotation,  5,6,  398;  effect  of,  on  winds, 
258 ;  effects  of,  7. 

Royal  Gorge  of  Arkansas,  326. 

Russian  plains,  75. 

S. 

Sacramento  River,  321. 

Sage  brush,  343. 

Sahara,  282. 

St.  Gothard  tunnel,  107. 

St.  Helena,  124,  175. 

St.  Lawrence  system,  155, 167,  329-334. 

St.  Louis,  312,  376. 

St.  Paul,  310,  312. 


St.  Petersburg,  376. 

St.  Pierre,  destruction  of,  113-114. 

Salem,  224. 

Salines,  87,  169,  170. 

Salt,  170,  410;  deposits  of,  167;  in  ocean^ 

179,  180. 
Salt  Lake  City,  164,  315,  324. 
Salt  lakes,  87,  163,  324. 
Salt  marshes,  216. 
Samoa,  typhoon  at,  271. 
Sand  bars,  213. 
Sand  beds,  409,  410. 
Sand  dunes,  desert,  88;  seacoast,  215. 
Sand  plains,  149. 
Sandstone,  33,  35,  409,  410. 
Sandy  Hook,  213,  215. 
San  Francisco,  278,  316,  376. 
San  Francisco  Bay,  208,  321. 
San  Joaquin  River,  321. 
Sardinia,  25,  207. 
Sargasso  Sea,  192. 
Satellite,  6. 

Saturation  of  air,  244,  245. 
Savanna  belts,  283. 
Savanna,  flora  of,  342. 
Savannah,  306. 

Scandinavia,  peninsula  of.  25,  208. 
Scenery,  western  United  States,  316. 
Schist,  34,  35,  413. 
Schools  of  forestry,  350. 
Scoria,  122. 

Scran  ton,  109,  309,  376. 
Sculpturing  by  rain,  51. 
Sea  breezes,  256. 
Sea  caves,  211. 
Sea  cliffs,  211. 
Sea  coast,  changes  in,  204. 
Sea  Islands,  215. 
Sea  level,  8,  179. 

Seasonal  temperature  range,  243. 
Seasons,  explanation  of,  398. 
Seattle,  316. 
Sea  water,  composition  of,  179 ;  density 

of,  181;  pressure  of,  181. 
Sedimentary  rocks,  32,  408-410. 
Sediment  in  rivers,  51,  52. 
Seeds,  distribution  of,  345. 
Selective  scattering,  233. 
Seneca  Lake,  153,  303. 
Shale,  33,  35,  409,  410. 


INDEX. 


465 


Sheets,  intruded,  34,  127. 

Shelter,  372. 

Shore  lines,  203-225;  abandoDed,  220; 
importance  of,  203;  lake,  162,  220. 

Shoshone  Falls,  320. 

Siberia,  frozen  soil  in,  19. 

Siberian  plains,  75. 

Sicily,  25,  207. 

Siderite,  408. 
sierra  Nevada,  99. 

iilicious  sinter,  410. 

Sill,  34,  127. 

Simplon  tunnel,  107. 

Sink  holes,  60. 

Sinking  of  land,  24. 

Sirocco,  289. 

Sky,  color  of,  233. 

Slate,  413. 

Sleet,  249. 

Sling  psychrometer,  423. 

Snag  Lake,  121. 

Snake  River,  320. 

Snake  River  valley,  lava  plateau,  125. 

Snow,  249;  measurement  of,  424. 

Snow  crystals,  249. 

Snow  field,  137. 

Snow  line,  96. 

Soil,  16;  glacial,  154;  importance  of, 
to  plants,  338;  lava,  130;  New  Eng- 
land, 299;  residual,  43. 

Solar  system,  3;  heat  in,  9. 

Solid,  19. 

Sounding,  174. 

South  America,  24;  coast  of  western, 
20<3;  fauna  of,  363. 

Southeast  trades,  259. 

Southern  ocean,  26;  weather  of.  29S; 
winds  of,  261. 

South  magnetic  pole,  418. 

South  temperate  zone,  climate  of,  293. 

Spain,  peninsula  of,  25. 

Spectrum,  colors  of,  232. 

Sphagnum,  168. 

Spits,  213. 

Spread  of  animals,  360. 

Springfield,  300. 

Springs,  59. 

Spring  tides,  189,  417. 

Stacks,  223. 

Stalactites,  60.  409,  410. 


Stalagmites,  60. 

Standard  time,  404. 

Stars,  3. 

Steppes,  76,  285 ;  flora  of,  .'^42. 

Storms,  262-271 ;  cause  of  cyclonic,  264; 
cj'clonic,  262;  paths  followed  by,  264; 
in  south  temperate  zone,  293. 

Straits,  cause  of,  207-210. 

Strata.  32;  disturbance  of,  36. 

Stratified,  32. 

Stratified  drift,  149. 

Stratus  clouds,  248. 

Streams  in  ocean,  191. 

Striae,  142,  153. 

Stromboli,  113. 

Struggle  for  existence,  347. 

Subarctic  climate,  285. 

Subtropical  climate,  285. 

Subtropical  flora,  342. 

Summer  weather,  eastern  United 
States,  291. 

Sun,  3,9,  10;  apparent  movements  of, 
397;  distance  to,  5 ;  effect  of  position 
on  temperature,  239;  heat  from,  10. 

Sunlight,  importance  of,  to  plants,  337. 

Superimposed  rivers,  83. 

Superior,  313 ;  Lake,  161,  162. 

Surf,  185. 

Sur\ival  of  fittest,  347, 

Susquehanna  River,  329. 

Swamps,  74,  167-170;  cause  of,  167;  ef- 
fects of,  170 ;  lake,  165 ;  mangrove,  217. 

Switzerland,  people  of,  388. 

Syenite,  411,  412. 

Symmetrical  folds,  37. 

Syncline,  37. 

Syracuse,  220,  303. 

Systems,  mountain,  94. 

T. 

Tableland,  83. 

Tacoma,  316. 

Talus,  44,  97. 

Tanganyika,  Lake,  162. 

Tasmania,  25. 

Temperate  zones,  man  in,  385 ;  climates 
of,  285-293;  fauna  of,  356;  flora  of, 
340. 

Temperature,  daily  range  in,  241 ;  differ- 
ence in,  on  earth,  239 ;  effect  of  altitude 


456 


NEW  PHYSICAL   GEOGRAPHY. 


on,  240 ;  effect  of,  on  animals,  353 ;  im- 
portance of,  to  plants,  33<) ;  influence 
of  cyclones  and  anticyclones  on,  265; 
measurement  of,  420;  of  ocean,  182; 
seasonal  range  in,  243;  in  temperate 
zones,  285. 

Terminal  moraines,  139,  148. 

Terraces,  river,  63. 

Thaws,  289,  292. 

Thermograph,  421. 

Thermometers.  420. 

Thousand  Islands,  330. 

Thunder,  268. 

Thunderstorms,  267,  268,  280,  289,  291. 

Tidal  currents,  187,  188,  210. 

Tidal  range,  187. 

Tides,    187-190,"  416;    effects    of,    189; 
work  of,  210. 

Till,  142,  152. 

Timber  line,  96,  343. 

Time  and  longitude,  404. 

Toledo,  166,  313. 

Topographic  maps,  use  of,  432. 

Topography.infiuenceof  on  climate,  279. 

Tornadoes,  268,  289. 

Toronto,  166,  313. 

Torrid  zone,  climatic  belts  of,  279-284. 

Trachyte,  411. 

Trade  winds,  259 ;  belts,  rainfall  of,  280, 
281 ;  desert  belts,  281. 

Transparent,  234.  ^ 

Trap,  411. 

Trenton,  75. 

Tropical  fauna,  .357. 

Tropical  flora,  342. 

Tropical  zone,  man  in,  386. 

Trough  of  waves,  185. 

Troy,  303. 

Tufa,  409,  410. 

Tulare,  Lake,  67. 

Tundra,  76,  168,  340,  384. 

Tunis,  peninsula  of,  25>  207. 

Tuscarora  deep,  175. 

Typhoons,  269. 

U. 

Underground    water,  19,   50,  59,    132; 

work  of,  39. 
Undertow,  185,  210. 
Ungava  Bay,  tides  of,  187. 


United  States,  physiography  of,  298- 
317 ;  reasons  for  development  of,  390- 
392;  rivers  of,  320-3;i4;  western,  314. 

Unsymmetrical  folds,  37. 

Utica,  303. 

V. 

Valley  breezes,  256. 

Valley  glaciers,  137-142 ;  distribution  of 
141;  former  extension  of,  141. 

Valleys,  filling  of,  67 ;  young,  55. 

Vapor,  15,  19;  measurement  of,  423, 
424 ;  water,  230. 

Vaporization,  heat  of,  238. 

Venezuela,  plains  of,  77. 

Vernal  equinox,  400. 

Vesuvius,  115-118,  123,  129. 

Vicksburg,  61,  328. 

Victoria  Nyanza,  162. 

Victoria,  peninsula  of,  25. 

Vienna,  376. 

Volcanic  ash,  34,  112,  122,  412. 

Volcanic  bombs,  122. 

Volcanic  cones,  forms  of,  .123. 

Volcanic  plug,  126. 

Volcanoes,  101,  112-130;  cause  of,  125; 
distribution  of,  123 ;  importance  of, 
129;  in  sea,  denudation  of,  129;  life 
history  of,  128;  materials  erupted 
from,  122. 

W. 

Warm-blooded  animals,  353. 

Warming  of  air,  238. 

Warming  of  land,  237. 

Warming  of  water,  238. 

Wash  deposits,  139,  142. 

Washington,  75,  102,  307. 

Wash  plains,  149. 

Water,  18,  19;  forms  of ,  244-250;  influ- 
ence of,  on  climate,  277 ;  need  of,  by 
plants,  337;  underground,  19,  39,  50, 
59;  warming  of,  238. 

Waterfalls,  53;  of  glacial  origin,  155. 

Water  gaps,  95,  103,  309,  391. 

Water  hemisphere,  27. 

Water  plants,  344;  texture  of,  339. 

Water  power,  effect  of  glacier  on,  155; 
New  England,  299,  300. 

Waterspouts,  269. 

Water  vapor,  230. 


INDEX. 


457 


Water  wave,  hurricane,  271;  volcanic, 
119. 

Waves,  accompanying  hurricane,  271 ; 
earthquake,  186;  iceberg,  186;  wind, 
184 ;  worlc  of,  210. 

Weather,  275-295;  desert,  282;  eastern 
United  States,  summer,  291;  winter, 
292 ;  influence  of  cyclones  and  anticy- 
clones on,  265;  southern  ocean,  293; 
vane,  420. 

Weather  Bureau.  426.  » 

Weather  maps,  426. 

Weathering,  38-44;  agents  of,  38;  aid 
of  organisms  in,  40;  results  of,  42; 
influence  of  underground  water,  39; 
rate  of,  41. 

West  coasts,  climate  of,  286. 

Westerlies,  prevailing,  260. 

AVestern  America,  coast  of,  206. 

Western  United  States,  314 ;  mineral  in, 
108;  volcanoes  iij,  124,  125. 

West  Indies,  20,  98,  297,  222;  eruptions 
of  1902  in,  113. 

West  wind  drift,  193. 

Whitecaps,  185. 

White  race,  382,  383. 

Wilkes  Barre,  109,  309,  376. 

Wind-formed  current,  186. 

Wind  gaps,  104. 

Winds,  255-262;  aid  of,  in  distribution 
of  animals,  3()0,  362 ;  aid  of,  in  spread-  i 
ing  plants,  345,  346;  as  barriers  to 
spread  of  plants,  346;  cyclonic  storm, 


289;  influence  of,  on  climate,  278;  In- 
fluence of  cyclones  and  anticyclones 
on,t265;  measurement  of,  422,  423; 
monsoon,  256-258;  prevailing  west- 
erly, 260;  relation  to  air  pressure 
255;  trade,  259;  variable,  prevailing, 
westerly  belt,  289. 

Wind  systems  of  earth,  258. 

Wind  waves,  184. 

Wind  work  on  deserts,  87. 

Winnipeg,  Lake,  162. 

Winter  weather,  eastern  United  States, 
292. 

Worcester,  300. 

Writing,  development  of,  379. 


Yellow  race,  382,  383. 

Yellowstone  Falls,  326. 

Yellowstone  Park,  316,  326;  geysers  of, 

132;  lava  of,  126. 
Yellowstone  River,  325,  326. 
York  Peninsula,  25. 
Young,  care  of,  by  animals,  360. 
Young  coast  line,  221. 
Young  mountains,  102. 
Young  plain,  79. 
Young  stream  valleys,  55. 


Zone  of  fracture,  18. 

Zones,  of  animal  life,  364 ;  of  beat,  275. 


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